This thought came to me while I was asleep (I don't know why this is what my brain resorts to when I sleep... but I digress).

For the tank mount, instead of making it 200/200 for the mount, what if it was incentivised a bit more. In the case of BOTH the WAR and the PLD mounts, what if:

50/200 You get the base mount, as it currently appears.
100/200 The mount receives visually upgraded in some way. Perhaps a more ornate saddle or something.
200/200 You mount receives yet another visual upgrade. Perhaps armor of some sort.

I feel with more of a tiered approach, people would be inclined to continue tanking longer, and you could actually inflate the numbers a bit.

Perhaps make base 100, secondary 300, and top 500 (like the commendations). This would give Tanks a bit of a break, but yet keep them in the Tanking business even longer overall.

Tanks get a mount, and a reason to continue tanking... and everyone wins.

Now please tear my idea apart, and make it better.