Summoners don't get benefits from intelligence.
If you have 10 in summoning your minion becomes a big demon and their infusion skill gets really good but they are probably bugged and they based damage is like the level one minion.
With a summoner you can get point into hydro (healing and support skills don't scale of intelligence either), so you can have a summoner healer and have any weapon or gear you want since you can distribute stat points as you like.
