She is not a bad tank, and she is absolutely not useless past 35. Barring spoiler information that I'll avoid, I used her everywhere I could and I still use her to tank my dailies on Illum. She does just fine. And yes, I took down golds 3 levels higher than me with her on many occasions. She may not be perfect, and may not even stack up against the others for all I know, but please stop spouting BS claiming that she can't tank X or Y, or that she's "useless".

Except it's not 10% less time spent traveling. It's 10% base speed improvement, putting you at 200% speed total. Compared to the 190% you're already moving at with the first speeder, it's only ~5% faster than you would have been moving if you had just stuck with rank 1. I'm with the OP on this. The additional protection is nice, but the speed difference is pathetic.