I've had this kinda problem too before. I think we all have.
I think there's a few key things that help: ooc consent and ooc coordination. If some guy on the IGS I've never met before, and neither has Triss, starts calling her out, I'm going to assume the worst about them. Because they're going into dangerous, murky territory, and I don't know if I can trust them. And because I haven't consented to this type of RP with this person. It's not a nice thing to do. It's not a fair mindset. But - what if I'm not receptive to adversarial roleplay? They don't know that unless they talk before they try something so volatile.
I like to know the other party well before I try something new and risky like that. I like to know how strong their IC/OOC separation is. For my own selfish sake, I like to have a gentle sense for how they tick, what they enjoy, what they don't, whether they're happy or not. I think "good" adversarial RP is more difficult and challenging than normal RP, so I like to be as well informed as possible so I can be a good partner. And so I can trust in my other partner.
I try not to think about a good adversarial relationship as being about winning or losing. I like to think of them as a journey, with new and different ways to explore characters, and new and different avenues to let them change. The fact that Triss is a DUSTer and therefore super strong/powerful is a sidenote, in my opinion. It's only one of the layers or levels that conflict can happen. What's more important is - why is there a fight happening? What will happen as a result of the fight? How do characters feel before the fight? After the fight? Was a fight really the best option?
If you win a battle for the wrong reasons, in character and in life, that's worse than losing a battle for the right reasons. The first might be a physical victory but it's a character defeat. The second gives opportunity to try, try again.
Let me call out to @Syagrius. James and Triss don't get along well, as Triss is poor in diplomacy and politics, which James is stronger at. It reflects poorly on Triss as a person and as a professional. That's such a unique and wonderful dynamic. His player has strong separation too. Thank you, my friend.
I think I take it too far. Probably the only two things people absolutely need are consent and coordination for, yes, boundaries, like you said Gesakaarin. What kind of set boundaries have you found that work well for all parties involved?