My experience with the Ardent is that it's not as good as the other Leader classes (likely due to receiving far less support).
Yeah, I thought of it more as a "beginner" class for this player because it largely uses At-Wills (with psionic augments.) I honestly don't know if the player would be able to run anything better. But she's having fun. Honestly, I don't include her when computing the encounter budget, and everything works fine.
Not having a Defender is a big problem, unless you have good Controllers.
We have one good controller - but she can only do so much.
Our first defender left to start her own group with friends from school (which is awesome to see the next generation taking the lead). We persuaded our second controller to switch to a fighter - but she's been unreliable in attendance.
Current party configuration is Wizard, Cleric, Avenger, Hexblade, Ardent, and sometimes Fighter. Pretty much the first four do most of the heavy lifting in the encounters.
But this not being able to nova hard enough, I'm flabbergasted by.
They're used to 5e. In 5e you can burn through every spell, class feature, etc., in a single encounter. You can't do that in 4e. You are fed powers piecemeal.
An equivalent 5e character could use every Encounter power in one fight, burn through every Healing Surge, etc. They don't seem to understand "there is a hard limit to 3 heals per fight." There isn't a wand, cure potion, lay on hands, etc.
Because of the less than optimal way they are playing, 4e actually feels more like a "grim survival" version of the game. They can't get full heals. Their resources don't replenish as easily. It's actually worked the best for dungeoncrawling than any other system I've used for this group.