I agree.
Not all heroes are good heroes. You want heroes with good synergy/ compatibility on the same team.
Even bad heroes can help you. Either Grave damage ( Note 3) or double strong color, or double strong color with double neutral color ( ask your alliance teammates about doubling heroes ). So you want two good rainbow teams.
For Rare events do you mean Challenge events ( Pirates, Guardians, Knight ) or quests ( Frostmarch, Farholme, etc. ) ?
I don’t even bother with the Challenge events ( Pirates, Guardians, Knights ) the rewards are so poor for the time, energy, and battle items spent. I just take the free world energy flask and spend it on the map.
If you mean quests ( Frostmarch, Farholme, etc. ) I agree with Dante that all healers are not created equal.
4*, 42% heal ( Note 1)
Rigard- cleanse !!!
Melendor- debuff
Sabina- debuff same color as Rigard
4*, 27% heal with 3 turn buff
Kiril- defense+ offense ( take that Vampire Lords )
Boldtusk- offense only
3* 32% heal with debuff
Belith
3* 32% heal with high attack stat
Hawkmoon
I often run two healers during quests, but make up for it with Wu Kong ( Note 2).
Friar Tuck works best as a 3* center healer for raid/ war defense teams, replaced by 4* Kashhrek, then 5* Guinevere. But I leveled my Melendor first since he can get me Rare Ascension Item Quests while Kashhrek only helps passively ( I want Guinevere, but don’t have 24 poison darts to level four 5* yellows. The three 5* heroes for rare quests/ titans/ challenge events plus Guinevere on war/ raid defense ).
Note 1
Note 2
Note 3