No warp charge cap, I don't even play with psykers.
-IF- there is a problem with psychic powers its not warp charge, its just 1 power. Summoning. Maybe limit how many times it can be used, or how many models it makes, or change its cost. Give it a scaling cost so its 1
WC the first time its cast a round, 2 the second, 3 the third etc. Summoning more daemons makes the warp less stable in the area, something silly.
I thought malefic powers already had bonus chances of periling?
it's also worth noting that the frontline gaming report posted
http://www.frontlinegaming.org/2014/05/24/warhammer-40k-7th-ed-video-bat-rep-daemons-vs-imperials/
the demon player did not win, it was a draw and the marine list was pretty mediocre.
Also, the guy rolled ridiculously well, someone mathed out what his rolls were and his first turn summoning rolls only had a 7% chance of getting those good of rolls, or in other words he rolled in the upper 93% of what he could roll, that's well above average.
i fail to see how this is broken in any way honestly.