Weighing in on this topic just a bit:
There's no doubt Kheldians can be strong on their own. But let me ask if they can be strong WITHOUT inventionsets and/or heavily specialization? Because no matter what some people think. I'm pretty sure the homecoming devs are still balancing this game around SOs per-the live devs (thus, also why so many things can become an easy faceroll). And the disparity between Kheldians and SoAs are pretty massive if you do some power values comparison. From what I can see, SoAs have melee on par with stalkers, ranged on par with corruptors, armor on par with tanks, and buffs/debuffs on par with defenders, and SoAs similarly were built with a 'jack of all trades' role in mind with a permanent specialization at level 24 (which can even be completely ignored), and their means of doing are much more favorable in the forms of team buff auras that also help the SoA's own survivability, all on top of SoAs lacking a special weakness like Kheldian ATs (you want balance? call me when Arachnos pays an independent contractor to flip a very big middle finger to SoAs to 'keep them in line and remember who their boss is')
Now, enough fist shaking at SoAs, some of my own thoughts on how to improve Kheldian ATs...
First thing that might help is adding a second debuff to their attacks, -tohit for PBs and -Dam for Warshades. Conceptually, a PB's blinding light striking foes leaves their senses too dazzled to accurately retaliate, and a Warshade's former life as an essence draining parasite means all their attacks still siphon strength from foes. Mechanically, this means Kheldians have improved survivability by reducing incoming damage, further, this makes them a stronger team player, with their large number of attacks (and especially if we could extend the timer on just how long their debuffs last) PBs could utterly destroy an enemy's ability to evade or hit back, while Warshades would neuter enemies that might run as well as their ability to even hurt opponents with now anemic attacks.
Second idea, which could be used in conjunction with the first, is to take a page out of the fighting pool and have Kheldian powers possess synergy with one another. Have certain power picks strengthen Dwarf and Nova forms while picking Dwarf and Nova could provide strong benefits back to human form, I'm hazy on numbers or details, but this could encourage more taking up forms a bit more.
Admittedly, the detoggle is another problem that needs to be addressed, and I really don't think "lol, learn to macro" should be the only solution to make it manageable. Because, once more, it sort of pushes Kheldian players into needing go increasingly out of the base game just to be enjoyable as other ATs.
Also, as a side, besides their lethality to specific teammate(s), I've always been fine with the extra spawns of void hunters. Better than fine in some cases, they will spawn beyond the spawn limit, and that means more EXP and loot! Why would anyone complain about that? Well, besides the kheld players themselves who would be understandably PO'd from getting smacked in the face by a powerful attack (that some people say they want to be irresistable) they have no means to reliably take out of the picture. Combine with being a Kheldian running a malta mission, you're basically boned as even a warshade can only use their hold on the sapper or void hunter.