I am getting irritated with Summoner in endgame content

[Maelwys]

and like I said your damage is INFLATED by the first pack of spiders which blm can spam flare on but summoner isn't going to bother expanding any real resources on killing.

I wouldn't worry too much, it tends to balance out.

Dropping Shadowflare on those spiders counts for a fair bit, and you can always use Bane to spread your DoTs to the Knights... trying a Flare or three on a Soldier is usually not going to end very well due to reflective stoneskins. One of the better strategies for P5 involves bunching everything behind the dreadnought and bane-ing everything, then popping the AoE LB when they're low enough = clean slate going into P6