If it's free, it doesn't really matter how small it is at later levels, because it's still better than what you had before. It might matter at level 1 though, especially taking into account multi-class dipping.
If there is an opportunity cost, e.g. sacrificing one attack to get it, then I can see how someone might want to consider balance issues but I would have thought that you would only want to sacrifice one of your attacks where it was worth it, e.g. where practically surrounded or where the enemy's damage potential is high.