Difference i think is buffs vs debuffs, a debuffs potency does so much more and applies to everyone while a buff while potent wont be as big abd its only (initially) limited to a party, add in just how big that bonus vs say a dunna ontop of what you stated with pet DT, makes idris one of the bigger increases compared to say brd or cors bumps
Not to mention the buff aspect of bubbles which also get a significant increase, but debuffs are/were the main draw from bubbles