The rating system is better for paintings/drawings but not so much for Lego. Impact and technique are useful but vision and originality are not as important. I'll start with these 4 and add my own categories for ratings after.

Originality:
Not many bio builders build animals. Most build humanoids. So the points for this category comes from going against the norm and doing it fairly effectively.

Vision:
While it has feline features, this is not instantly recognizable as one. It does look like a beast, but the feline features take a while to notice. I'll go more in depth below.

Technique:
The techniques used here are good enough to hold it together, but there are too many parts that seem to only be used to add more pieces. If the size vs supply limit is the problem then making this smaller may be the better option. Again, more on this below.

Impact:
The shape and colors used make this 'pop' enough to draw attention, but not enough to keep the attention for long. Large MOCs usually grab the attention of kids, but an interesting MOC grabs everyone's attention. Once again, More on this below.

These are my categories of importance:
Shaping: 2.5 stars
You are able to shape you parts to fit the correct profile better than most, but you use too many filler parts instead of using the shape of the pieces themselves. As I said before, If the supply of pieces limits the piece use, then make this smaller to be able to better use the pieces you have.
Areas, such as the ankles and wrists, shouldn't be as bare compared to the more filled in chest limbs. The thigh should also have more of the mass than any other part of any limb. This is where the strength of the animal really shows.
Adding ears can help shape the head and give a distinction of where the head ends and face starts.

Anatomy: 3 stars
The anatomy is good enough to know it's a feline, but the proportions are off. All of the limbs are far too long. Shortening each by 8-10 studs would put it back into the right proportion. For the front limbs, the forearm+foot should bet he same length as the upper arm. For the back limb, everything past the knee should only be slightly longer (almost unnoticeable) than the thigh.
The chest is off too. The length of chest top to bottom should be the same size or longer than the shoulder width. This will give you the slender catlike feature you want. Many builders make the chest too human-like and it doesn't work for animals. The chest and stomach between the limbs can be fatter but shouldn't be much bigger than the shoulder width.
The neck needs to be longer. Roughly the length of the head itself. And the torso needs to be shorter by about the same length. Moving the shoulder location back should fix both at the same time. The eyes also need to be a bit more forward. Keep them under the crown as you have them, though. And the tail needs to be longer and thicker. A different technique might be needed for that.
I usually find a picture of the bone structure of what I'm making so I know the size proportions and joint locations.

Silhouette: 3 stars
A strong silhouette can amplify everything about a model. If the shape of the whole model is recognized correctly (in this case a tiger) then features are spotted easier. The silhouette for this model is a bit fuzzy, but still cat-like. Fixing the anatomy and shaping can strengthen the silhouette. Also taking out parts that break the shape of the MOC up can help as well. For example, the spikes above the pelvis break the shape you were going for and substitutes its own shape. Same with the large fins on the neck. The disks on the thigh also seem very out of place.

Color Blocking: 2 stars
Silhouette and Color Blocking can go hand in hand. The silhouette of a block of color should be able to be distinguished as a shape and not a Lego piece. If it isn't then it runs the chance of camouflaging the shape you are trying to create. This camo effect can be seen in the cheeks, thigh, and upper arm. Keeping solid colors in those areas might serve you better.
The head has a large feline shape which is good. The bright green crown piece is a nice fit. It can even work for the cheeks, but the other bright green pieces distort the shape you were going for. It's like one piece is fighting the next to be seen. You end up hiding the chin, snout, and eyes, which should've been the stronger features.
Keeping the shoulders a single color can help distinguish it as a shape rather than blending in with the chest/stomach. The same can be said with the thigh and all other parts really. This is important because you want the viewer to see where each part starts and finishes. It helps recognition. Use color to distinguish parts. A line down the back can accent curves. Coloring the stomach can give the limbs/neck a better contrast to immediately show what they look like. The same goes for tail, crown, and paws. This is a general rule for color blocking rather than something specific for this model, but it can help if this is all kept in mind.

Interesting-ness: 3 stars
This is a weird field but important nonetheless. A well made model can be completely uninteresting and in turn might not be liked. An interesting subject will grab more attention than one that is not. A bionicle tiger in this case is much more interesting than another bionicle humanoid. The effectiveness in which you achieved building the tiger can use work; meaning if you worked on the above critiques, you can make this MOC much more interesting.


Sorry for the wall of text, but I tried to be as detailed as possible with the categories. I use 3 stars to mean average. 1 means awful and 5 means beyond amazing.
I don't expect you to work on all of these elements at once. I practiced each of these one at a time and only combined them when I felt comfortable. In future MOCs, try working on any one of these and you'll see a significant difference.
I can clarify any of these or be more specific in a section if you'd like. Feel free to ask any me any question or message me if you need help or advice on a future MOC.

~Mike

Having watched the creation of this behemoth from the start I can say I'm as proud as 3rdeye is of this wonderful beast.
I don't know what to say apart from the fact that this is awesome, so I'll stick to simple pros and cons.
So the positive things I can say about this do far outweigh the negative. The positive being:
- Overall form. Looks catlike, nice range of poseability.
- The head. As others have said, this is probably the best section of the MOC because we can see that it's the head of a large cat.
The large green piece works well to give an impression of 'spiky fur'.
- Chest vents are rather a cool idea.
- Stability. He looks like he doesn't fall over easily and is.. well, stable.
- Colour. It works as a sort of 'forest camouflage'.
- Bio. The whole idea that the rhotuka spinners double as propellers is nice.

Negatives...
- Front claws a a tad weird and gappy.
- Ehlek spines don't work too well. They're either too far apart, or there isn't enough of them. If you have to have two, place them either side on the upper back. Would add to the strong-large-cat idea- spines on the back are cool, but they need to be placed right.
- Tail is a bit out of place ( not many other plain green parts) and needs an end of some sort. It should also be a bit thicker and maybe longer considering the rest of the animal.
- The rhotuka spinners should probably be a bit less stick-y out, and would probably look better as long vents similar to the vents on the chest- the rhotuka discs could be on the 'receiving end' of the vent and they could be placed on the back. Bear in mind though that this is simply a suggestion.

So overall, a great moc that's been well built, but suffers from some minor things like the tail and the placement of the spinners.