There are a number of sets which stack on additional things for a powerset. Sometimes it is stacked, comboed, etc. Here's the problem I am seeing with Insight.
1. It feels random when it triggers. I have done attacks chains, or even cleared a mob without getting it or at best it kicks in on the next to last attack.
2. The player can be locked out from gaining Insight. Not that this is unique as Savage does it similar in that regard. At least with Savage there is a clear pathway to building it back up and there is even Blood Lust to pop it back to max. Here, you can be locked out and not know when you are getting it back.
Ultimately this is about a set's feel. I can plan out and get a feel for a number sets because I as a player feel like I have control over the situation. I can figure out how I want to use my attacks in the best and most efficient way. With Psionic? It's just attack stuff and maybe it works out. Odds are you will overkill things at random times.
Solutions:
1. Have Concentration give Insight. Why oh why was this not the default? One would think you would have insight after concentrating on the battle.
2. Concentration/Insight is a toggle similar to DP or Staff. I'm fine with it using end.
3. Concentration/Insight is similar to Rage in that it is a long term buff.
4. Concentration/Insight is similar to Power Siphon. The more one concentrates, the more of a benefit there is to Insight.
Pretty much at this point any working of it would make the set feel better, but I would lean on item 1 or 2 with maybe 2 being the best. I'm still leveling. Things might change, but right now Psionic Melee doesn't feel smooth at all. Even if it is balanced partly with how it is or isn't resisted, it does not feel fun currently. It feels clunky.
EDIT: With added info below about Boggle, I would shorten the animation and make the Boggle AoE flagged with the Confuse ST.