The biggest problem with new players has very little to do with the fact that they're new to the run. In fact, the real problem isn't even related to new players. The problem lies with the fact that people aren't observant. They aren't seeing what enemies are doing, they aren't seeing what their abilities are particularly good for. They rush in without any actual thought. This is the problem.

If you're a Paladin and you hit Haukke Manor for example, by that point even if its your first run, you SHOULD know how not only combos work, but how enmity and enemy positioning is solely dependent on your aggro abilities, but more importantly, you have access to Rage of Halone, which is the ending of what is now your best aggro generating combo, and yet I still see plenty of tanks in that same general area not using flash, not alternating between enemies while rotating through their combos or even using the previously mentioned one, but instead sticking to Riot Blade.

It shouldn't take you 20 runs. It shouldn't take you 10 runs. It shouldn't even take you 2 runs. All it takes is being observant, and actually spending the time to look at available actions and their properties to have that "ding!" moment. "Hey, this succubus-thing uses some kind of AoE that freezes whomever is nearby and does it predictably. I have a stun ability, maybe I should.... Oh hey! It worked!"