I love where you are going with this but like Sypher said they need to focus their role and not let them be jacks of all trade master of none like in FFXI.

Either make them full fledge DD/crowd control/debuff OR Healing/Support/Off tanking. Not everything depending on the summons so that they are overpowered and then nerfed to the ground and bad at everything.

To bring up the idea of mastering, this could be a good opportunity to apply it. Like you decide to get the SMN job but you get to master either the DD side of it or the Heal/Buff side of it. So you can have DD summoners and Healing/support Summoners. Always with the option to go through a quest to unmaster and change path if you decide you don't like it.

Each summons could have various DD, Crowd control, heal, Buffs, Debuffs bloodpacts (for need of a better name) but depending on what path you chose you are effective in only those you master.