Id agree summoner isnt a Wow Affliction Warlock (Dots) but it probably should take a ton of lessons from Deononology Warlock which is a lot of fun to play.

As for smn's urrent design i honestly think adding more summons would amount to no change at all. Same as adding Temu Bahamut changed nothing, bar making things awakward. Im not saying redesign the whole concept, but it definitely needs some deep mechanical changes.