Someone correct me if I'm wrong here, but I think I figured out how to totally break 40k with summoning spam worse than any Daemons list could ever manage.
If you take an Inquisition detachment, you can grab an Inquisitor for 25 points, add Mastery Level 1 for 30 points, and then take three units of two acolytes and an imperial Psyker. Since the Psyker is ML1 whether or not any other Imperial Psykers are in the squad, (Brotherhood of Psykers has no minimum squad size,) you've essentially got tiny, crappy battery units. For 109 points, you get 4 Warp Charges.
Repeat Ad Naseum. In an 1850 list, you get 64 Warp Charges with a few points of change jingling around as needed (whixh you should use to take Coteaz,) and as many rolls on the Daemonology chart.
This means, in addition to the obvious, that somewhere around 10 guys are going to roll Possession. (And you're going to have easily enough Warp Charges to use 'em.) Cast all those turn one, you get 10 (Well, 7-8 once you account for failed tests and DTW, though if you pour more power into the spells then you'll be a bit more succesful but get less off, ) Greater Daemons. That's an entire 1850 army right there, generated turn 1, and you've still got 54 Psykers sitting around every single turn, utterly destroying your opponent's Psychic phase and generating even more units every turn.
Perils doesn't matter, since your units are dirt cheap and you only need to cast these powers once to get your value out of them several times over.
You can't really shut it down turn 1 with any kind of Alpha strike,(Unlike other Summoning lists) since it's so many small units rather than one big one, and Coteaz makes it difficult to get the first player turn. Killpoints is the only real threat, but with ten Greater Daemons coming in immediately, backed up with a lot of Psychic potential, it won't be unthinkable to wipe the enemy off the board. (And Killpoints is pretty rare these days.)
Then again, this list is incredibly boring, stupid, and tedious to play and even worse to play against, so run it at your own risk.