When you roll a 1 or 2 on a damage die with a Two-Handed meele weapon, that die is rerolled once.
And, as I already mentioned and gave example for, that is NOT sufficient to communicate what the feature is meant to do without opening it up to abuse or a lack of clarity.
Worded like that, it could easily be taken to mean ANY damage die you roll while you have a two-handed melee weapon, regardless of that damage's source or cause. That's not good enough.
Here's another example: You're one of the classes that can use your weapon as their spellcasting focus - and you cast fireball. Worded as you've written it there, I'd get to reroll all the 1s and 2s of my fireball. I don't.
Hueron is right though - as many of us have requested, and I'm pretty sure you and I both agree on, Rag, having a more robust combat log that actually gave all the relevant information clearly, all the time, would be beneficial in cases like this, especially to see exactly how something was working out in game, compar4d to our expectations.
