Thanks for all the advice folks! It hasn’t occurred to me that leveling my 3s would be remotely worth it once I got 4s! 
Not sure what you mean with the farming comments bud - how is a good character not just a good character (I believe you, I’m just asking the stupid question so I can understand)! 
Just got Friar Tuck in the event. That’s the healer sorted as Annie had pointed out to me! 
Farming is a term we use when you replay a level on the map. Sometimes you run out of items to craft stuff so you go back and replay levels to get the stuff needed. For example. You need lumber to craft an ax attack. You go back and replay levels to try and stock up on lumber. You will hear that phrase quite a bit.
Not the best- but he was the only healer I had for ages, and he served me well
Thanks Glenn, but why would the 4*s not be very good for this?
No one said that 4’s would not be good for this. I think they were saying to slow down. It’s up to you if you want to spend a lot of money and try to fast track the game. Nothing wrong with that. Most of us started out with 2 and 3 star teams and replaced them as we got better heros. What someone above was pointing out is the ease at which you can ascend a 3 star hero vs a 4. A 4 star hero will need 3 star ascension items for the last level. At this stage in the game you will not see them. A bane at 3/50 is pretty strong. Plus 3’s like Gunnar have wicked defense skills. Some of the strongest players in the game will still use Bane for 10 star titans. There is value in leveling 3’s up as well.