Whereas I agree with the summons being all rolled into one and just upgrading as you level in Arcana I don't agree on the % loss of HP and I don't agree totally with not being able to unsummon the summons while in combat because that would suck if you are trying not to fight the mob in general and your summons stays and keep you in a fight. This would make it so that to reset a fight for an infuser you would basically have to die or risk death more than other much stronger classes due to the fact that the infuser class is mostly reliant on it's summons for survivability.
Now I can say that while actually fighting that the summons should have to die while in combat before you can summon again but the in combat status should be determined by the frequency between your actual attacks on the mob that your summons are fighting.
An infusers summons are basically the backbone of the class and most of the skills or abilities the infuser has is about buffing and aiding the summons in the fight nerfing them or the abilities they have at it's current state would in my opinion make it not worth playing.