Usefulness of overcapped Summoning Magic

[Soranika]

Lengthening Blood Pact: Ward's duration
Increasing amount of MP gained through Elemental Siphon
Increasing potency of Avatar Favors

Those are the most important things Summoning Magic is use for, right? Before 76+ level capped, I obsessed over having high overcapped Summoning Magic, 317+ was very obtainable without keeping me from sacrificing important gear to have avatar favors more potent but now I'm like... meh, what's the point?

Right now my Summoning Magic sits at around 413ish and I often feel embarrassed when I see other summoners busting out 440+ but for what? Blood Pact: Ward's duration are still pretty mediocre at best. With the AF3 set, proper MP management, and refresh gear, there's no need to be overly cautious about how much MP you have left (unless in Campaign). And usefulness of avatar favors? Carby's for solo'ing, Diabolos if in a mage party of an alliance. I'd say Shiva or Leviathan but really, what do the other mages really ask for from a Summoner for support?

What's the practical use of having such high, over capped Summoning Magic? Or was did I answer my question already with a negative view of it and happen to be missing another important element?