Leinster got through last season without too many injuries (unbeaten for 14 games or something) and only went out of the ERC to Leicester away (the hardest draw they could have got). They don't have any more Celtic League games now either so that will lessen the chances of injuries.
Munster have a tough group too. They have to beat Gloucester at home now which I'd fancy them to do but it won't be easy.