Since no one specified their locations in relation to each other, it was left to me to do so, and it made the most sense to have Leeroy's guy approaching from the other side of Adrian in relation to Arty, since he could see both of them as he walked up. I described such an arrangement in my post, which means Adrian literally could not look at the lich without turning away from Arty, unless he moved before doing so, which he did not.
As for the body slam, yes, you remain largely unaffected when you're in the middle of a fight with the adrenaline already flowing and the expectation of getting hit, but that's not what's happening. Adrian is entirely unaware and getting blindsided by a 220 pound projectile slamming into his back at superhuman speed. That's going to knock the breath out of him at the very least, armor or not. You also didn't specify any unique functions of the armor, so it is assumed that it functions in a similar manner and at a similar temperature to normal plate armor, which also doesn't do great against blunt trauma (which is what Arty's attack is causing).
If you're going to use magical armor that burns everyone it touches and can instantly sprout spikes of hellfire all while completely negating kinetic damage, you really have to specify all that in your CS, otherwise it's little different than power-gaming.