Yup. Funny that the munchkins overlooked the WM loophole.
RE: Psion v. WM. In the battle of glass cannons (pick any blaster), initiative would determine a large % of wins. High Dex & Super Init FTW. A pure psion burns down pretty quick and has no Epic spells (Contingent Resurrection). A Cerebremancer (Wilder / Psion) build would have a lot more staying power bc of Epic spells.
The psion does have a very nice advantage that their best power is L1 and can be quickened. IGMS can't be.
WM would be Max IGMS + Quickened B-Bolt v. Twin, Max, Emp Crystal + Quickened Twinned Max, Emp Crystal. I don't recall getting quickened powers to work, so I never built them.
Just looking at the exchange of howitzer blasts, I'm wondering what Epic Dodge would do. IGMS is 20 separate missiles & 19 burn bolts vs. 6 psion ([Primary max + twin max + empowered]*2 ). The maxxed crystals hit for ~ 220 hp and the empowered ~ 190, so the defender would need half to miss AND have a crap-ton of hp.
W/o the WM loophole, the arcane blaster can't match the Psion types on raw damage.
One thing that really blows about psionics is that Maximize power does not operate on the Empowered bit, so there is a lot of lost damage potential. Max not working on Emp is the same for casters, but manifesters pay (d6 / pp) to upscale damage, where casters get scaling for free (d6 / caster).