No, invaders are also not affected by AI enemies. However, some enemy AI AOE attacks (like dragon breath) or environmental damage (like lava) will still damage invaders. But no, in general you want to stay the hell away from AI enemies. I talked about PvP generally earlier, and what I think most people need to have is a quickly accessible surprise. If you're a magic user, don't dress like one and telegraph by casting your orbs early as hell. If your primary is a large club, wait for him with a dagger in hand. Then pounce. Then we move to phase 2, which is pressuring the battle. I don't recommend healing as that authorizes healing on their part by the Unwritten Laws of Dueling. If they heal, then fuck it. You rarely want to go for combos, as they are a recipe for being parried by anyone with a bit of poise. Whatever your weapon is, learn the sprint attack, the roll attack, the jump back attack, the 2h options, and switch between them freely. Items that are disproportionately effective in PvP: small shields, esp. the heater shield, with bigger parry windows for the lag; the steel ring for boosting your ability to survive being nickel and dimed into the grave, the humble reinforced club and its ability to clean out poise in 1-2 2hr2 hits, 50% movement with better damage resist so you can't get one shotted (ie throw on some stone armor bits) as easily, and so on. Also, there's no shame as an invadee in using a souped up pyro glove or other "unsporting" move to clear out an invader; we're they're used to it, and it's all part of the game when you are the transgressor.