My cards aren't high level, so my knight is still missing the pierce skill. I do sometimes end up using him as a tank, but most of the time that'll be when I expect there might not be much magic attackers and for example with the super sneak rules.
Since my paladin is only level 1 I don't end up using him frequently at all, but yesterday I had a melee only and no armor game where I went Life for my quest and used paladin as a tank so he could take a few hits, with knight in second and then having the feral spirit and elven cutthroat with me too. So despite it being level 1, sometimes I still end up using it with its shield ability. I agree that he's more likely to be more useful once he gets that magic reflect.
Sacred unicorn ends up being my tank most of the time (when excluding neutral) unless healing isn't allowed. Crystal werewolf is sometimes added for the silence, but not frequently as the tank, I end up placing it last place sometimes so it can tank some sneak hits if the opponent brought any.