You didn't explore the evil side of the AE deeply enough. I spent a lot of time looking at the custom critter system and tested a lot of combos. Its hard to say what the worst possible combination was, but there were a lot of hidden nasties in there for people to run into that make storm summoning look like a squib.
Consider: Mind Control/Dark Armor. Its a ranged mezzer with confuse. Few non-melee can handle that very well. As for the melee? Dark Armor has Soul Transfer as a rez. Do you have mag 30 stun protection? How about mag 60 if you accidentally kill two a the same time? How about mag 90? And that's only after you get past a bunch of overlapping PBAoE toggles.
I had a list of combos to avoid when making real missions, and this was very high on the list. Its just too evil.
Along the lines of storm summoning, a combo that only scored 9.8 on the evil-o-meter that was similar but nastier was Earth Control/Cold Domination. Two autohitting patches - quicksand and earthquake - plus a rain, plus two really awful debuffs (benumb, heat loss).
Pretty nasty but I wouldn't have touched darkness with a 100 fool pole with the mobs I was designing, well, some of them, it was against the theme to an extreme. Honestly alot of powersets, the buff/debuff ones especially were especially bad when en-massed. The thing is the numbers that could be stacked in the debuff range, or the cc range, was unimaginably unforgiving, actually you could say it wasn't much different then dealing with a pvp 1.0 multiplier stacking team.
The reason I mentioned storm summoning was due to the fact that 8 tornados was pretty much death to anything and melee couldn't hit anything in 8 hurricanes, let alone with the -recharge stacking from 8 snow storms and -movement from that. Getting torn down to negative numbers by anything that can was generally bad.
Actually any CC stacked from everything on the map could probably over-run people pretty easily.
Combo's I used that killed fast; kin/sonic blast(fulcrum shift on all mobs). It had to be killed in moments, because the -resistance stacked a little harshly with the fulcrum shift damage buff. Set it as an ambush and leave the message off(and if your really evil, set the ambushes to minions). Said mobs also used /radiation blast alongside kin.
Any mastermind in an ambush; the mobs instantly bring out the henchmen. But thugs was especially
bad, super laggy and stupid fun about it, bring lots and lots of attackers as they'd instantly fire gang war off even before getting in range. No, I am not kidding about that. Once I tried spawning an AV to help another, unfortunately the stupid thing spawned 8 of them(and I THINK I gave these mind control). And they all had gang war fired off. Considering the AV I was fighting was an enemy with FS(and the full kinetics set)......:S.
Those were just a few things I did in the early missions, let alone later missions. I was honestly waiting for time manipulation to come along for those. But then I didn't want to go to brutal on players.
Wished I explored it more, just I had to keep in the theme of the characters. Darkness powers were universally only good for magic themed characters and mobs, mine were all technological/science based with only a few exceptions. I did however have other things to keep the difficulty rising for the archs, just needed the right sets to come out.