I'm saying a summon should have probably a cool down of 12-15 rounds with low int, and maybe 5 or 6 round cooldowns with high int (18-20ish). And the summons should probably all have their cooldowns tied together.
I never even remotely approached dealing 4-6k damage in a single crit, though yes I'll agree that summonns are fairly subpar when it comes to offense (though the skeleton summon can do some decent damage early on) o.O Admittedly, I didn't try all too hard to min-max damage (I didn't buy the stat bonuses multiple times, for example, and most of my characters were multiclassed so they didn't necessarily do the most damage with single attacks as they could). I do think some of your impressions of summons being weak is a matter of other skills being ridiculous or straight up broken. I hadn't realized the elemental shields straight up double your health until I used one in a mod. That just seems to be not functioning as intended and does make elementals seems kind of pointless as tanks for casters. My mages were also both GC (which is of course OP in its own right) so they only had 300ish health (playing on hard). I also agree that getting 50% block with a shield is pretty absurd. Lots of thing in D:OS are unbalanced, not just summons. And yes, they tend to be more useful in the beginning than in late game. But summons are kind of ridiculous, in my eyes.
One big way that summons are good "tanks" is that often enemies will go out of their way to attack them. So not only are enemies wasting AP on attacking them, melee characters have to run up to them, and if you position the elemental right, enemies can spend a lot of AP running to the summon, killing it, and then running to you. And you're right, exploiting the AI is kind of cheesy, hence enemies shouldn't be inclined to attack them unless they pose a threat. It certainly isn't easy to figure out what kind of situations enemies should attack summons and when they should attack the summoner, but I think Larian could figure something out to make improve AI behavior in this regard.
