You raise questions I hadn’t thought of before. I just assumed it meant “caster trinket, no warriors, hunters, feral druids or rogues.”
I have no idea what the answer to your question is. Thunderclap would probably count, but I would guess shield slam and shockwave wouldn’t. And now I’m thinking about feral druids, because none of their abilities are weapon-based, and who knows which ones count as spells, specifically the runes?
And which Paladin abilities are weapon-based? Like… judgement?
Maybe it means ones you can’t cast while disarmed? So shield abilities might work?
I hate that you’re making me think, now I need to know too.