Generally speaking this is what you should consider when maxing a 5-star.
Depending on who you have maxed on your 4-star bench you may want to look for who would pair and color stack the best with your 4-stars.
Having one or more maxed 5-star healers is a must if you want to be competitive in raiding in the 5-star arenas.
Healers can do their job perfectly well at 3-70 and their SS generally do not benefit from getting to 80.
Yes #2 and #3 directly conflict with each other. The issue is survivability of your healer in the top tier of raiding. A maxed 4-star hero generally has better stats than a 3-70 5-star. But 5-star healers generally bring more to the table than 4-star healers would. If you are a long way off from trying to stick in Diamond arena full time, just be content with opening Diamond raid chests.
I might max Vivica over Joon for those reasons and because she’s an OK tank if / when your alliance goes with yellow tanks. You’ll eventually want Guin maxed so that is strictly a temporary condition.
I don’t have Mother North but I have used Alby since he originally appeared. The revival ability is somewhat overrated if you are OK with some level of risk. Also, MoNo’s revived heroes aren’t exactly tough enough to really count on. Her healing however is pretty good and minions are a nice bonus. Evelyn will do OK at 3-70 for titan hits and can also pair really well with all your green hitters.
Santa is relatively useless outside of being a tank. “Relatively” depends a lot on who else you have on your red bench. Fast snipers and strong hitters will easily be more valuable to you than Santa. Neither Zim nor Mitsuko are worthwhile tanks though and if your alliance insists on standardizing on a red tank you could just say that this is the best you’ve got and hide Santa among the feeders.