You are perfectly right when mentioning that different champs are an obstacle to different playstyles. I do fully understand that.
Let´s say we have 4 major play styles in game these days (not counting variants and orchid builds). This is melee, DC casting, DPS casting and ranged. So if all champs would be powerpacks and be geared towards thwarthing one of these 4 basic play styles, I would fully expect to get into troubles with 1/4 of all champs I find. Once a little more, once a little less, but in average I would face 1 out of 4 champs on any given build to be a challenge. If we have more differenciation, we get 8 champ sets, so I would face 1 out of 8 champs to be from hell.
I currently get one out of perhaps 500 champs to be from hell. Most of the time, the champs are just bloated meat bags that last a few seconds longer than the rest. Depending on saves, even not the last mob standing.
What I do not like is the fact that champs in their broad mass do not pose a real challenge. Most of the time they are not even annoying. Except on a caster - because they need more SP. There are even champs beeing much easier to kill than their ordinary mob counterparts. If the broad mass of champs would pose a bigger challenge, but there would not be any possibility for the one champ from hell, it would be fine. Randomness is a good thing to have. But only if it runs within a certain bandwidth.