Let me give you a traditional EJ moderator welcome to new posters! Mostly traditional due to the nature of (most of) the new posters I'll admit.
Anyway, the question you asked already has quite some discussion on the matter, as could've been found out if you used search. If you need help using our search function, read this thread: How To Use Search
so this is my first time posting here and i was wondering if there was an actual armor pen cap because a guildie of mine was telling me there was one last night and he linked me this post MMO-Champion BlueTracker - 116% Armor Pen only giving 66%!?!?!?!. so if there is an actual armor pen cap wouldn't it be pointless to stack both grim toll and mjolnir runestone? my druidis at about 440 armor pen