I was really miffed when I found out that the Conjure Seeker spell is not affected by any of the Conjuration perks (Atromancy, Elemental Potency, Twin Souls). Not sure if it's affected by Summoner, but it seems that it is. Basically making the Seeker a bit crap. He also seems to have less hitpoints and does less damage than his counterparts in Apocrypha, not to mention the fact that he can't duplicate himself.
I'd simply like to address this issue.
If someone could point me in the correct direction, that would be great. I tend to learn by doing so doing it myself would be more beneficial to me than downloading a mod (which doesn't exist yet). My experience with the CK isn't great, but I know my way around forms and the object window. Unfortunately I have no clue as to how the perk effects interact with conjured actors, and I have zero experience with Papyrus.

You may have some mod messing with your iMaxsummoned value because I can swear i've had two seekers out before....

Yea, just checked in game by summoning one with each hand at almost the same time, you can have two.