The 75 ought to be noticeably better, but there is always the risk that it might not have you want on it. Although you CAN twiddle a legendary item to be more like what you want, the additional griind involved doesn't make that a particularly appealing prospect. So, I would say you are in the market for a new toy, but, as long as your existing one IS working for you, it is not high priority. Once RoR opens up to lvl85, tho, the pressure to update wll increase.
The tactical healing rating is the most important part of your healing book, just as tactical damage is important on your DPS/Soloing weapon, so you should try to get the highest level and age possible for those two. However, you can get by with older healing weapons and soloing books if they have the legacies you want. I have a 60 1st ager from Moria that has perfect legacies for healing, so I'll probably keep it for a while.