One gathers either he didn't inform his previous party what he was doing as support...
No.
One gathers that he was with his previous party from the beginning of their careers, so they had no basis of comparison for what it would be like without his support, and thus didn't grasp how much his actions impacted their performance. And they didn't believe that it was his actions rather than it being that they really were "all that."
This is the standard trope.
His current party has a far more realistic take on things.
Lloyd doesn't.
He thinks what he's doing is the bare minimum.
It's what you should expect of a support mage.
Which is also a standard trope.