Strange. At least Timeless Isle does give XP, however, I do not spend time on the Battlemasters, as they are a rip for the most part, and the benefits are not worth it. They should give Pet Charms, not crap.
I just don't see the point, beyond simply getting the Pets that you must (Water Spirit) and that's about it ... the other three don't even feature in just about any strategy around for anything, thus, I do not bother.
The same goes for the big Pet names in the Tanaan Jungle, and I would not mind doing them some more, except that the rewards are crap. In general, the folks that coded this lied to the user base, by continually saying that the harder things are the better the results and rewards, and instead they don't even give us a bone, or a hot dog so your pets can get 25% more experience while leveling, specially now that they took away the Pet Charms, with a malicious nerf to prevent you from spending time on something else, other than the Legion expansion.
For that matter, the first Pet I got in Legion from one of those class things, was with the shammie ... and I got a Level 1 Pet ... that has EXACTLY the same stats as almost any BEAST at level 1 as an Uncommon Pet. THAT IS NOT CALLED a REWARD. That is called false advertising and a lie!