It's probably a little on the underpowered side, I'd say (though other than putting a gestalt ardent//monk/atavist together for a PBP game that hasn't gotten off the ground yet, I've never played one); you're almost chosing your powers when you choose your mantles (most don't have a power at every level, and rarely have more than two powers at any level).
Well, as a proposal, we can either (1) accept as is, (2) reject, or (3) have someone propose a "fix" (as we did with the swashbuckler). The class may be underpowered, but the question becomes is it super weak, or just not an optimal choice?
My wife is playing an ardent now, since her Favored Soul took a greataxe critical at full power attack to the head recently -- the npc barbarian rolled two natural twenties in a row when he decided he was going to die and wanted to try and take someone with him!
I'm not sure if I like the ardent or hate the ardent, but I am sure it's an absolute pain to plan out properly. And the life mantle completely sucks for low level play, so don't make the mistake of thinking of a low level ardent as a healer!
Looks more-or-less fine to me. Compared to the Wilder, it has a similar number of powers but more restricted (though from a slightly wider list if you somehow get around the restrictions), though it gets new levels of powers more quickly, but it lacks Wild Surge. Seems good, so YES
Actually, it is the most versatile of psionic classes since you can basically MAKE UP your own mantles(The Mind's Eye: Expanded Classes, Part Four). Here's the lowdown:
1.you can add powers to any mantle so long as the total number of powers in the mantle do not exceed 10
2.only restriction to the powers added is it must be thematically appropriate. This is basically a DM's call thing. Some might allow you to add expansion into conflict-based mantle, some might allow those psionically crafted weapons, etc.
3.you can make up your own entirely from scratch by substitution so long as it does not directly offend your DM's logic ( no teleportation in natural world)
4.for coolness, you can exchange energy mantle for a specific elemental one(you can never take energy if you take a specific elemental mantle).
Also, there was some wyrd wording used when they described which powers they can learn. Apparently, they can learn any power that they can manifest. Now this only makes a smidgeon of sense IF the normal 'you can't spend more PP than you manifester level' doesn't apply to Ardents. Otherwise you'd be stuck with a ton of powers you couldn't cast till you get to a higher level. However, the book then goes on to say that the normal rules DO apply. As far as I know, there has been no errata so it is DM's call again on this one. Basically so long as you don't try to completely BS your DM Ardent can let you do anything another manifester can do almost as well AND do other things they could never do.