Nice selection, both of already maxed ones, and new ones to choose from.
If you didn’t already have Alberich I would’ve also said Heimdall. I’d kill to get any reviver… which surely is at least a little bit ironic, but I digress.
Personally given the rarity of mats for 5*, it’s not likely I’ll every max a duplicate 5*… but never say never I guess. But I wouldn’t go with the 2nd Lianna or Kingston, as good as those are.
If you particularly need more healers, I’d think about Ratatoskr. Not knowing anything else about your roster, I would seriously think about Zocc, I don’t have him but mana/special control is always useful. Also Atomos since his last buff is pretty devastating. So I’d pick one of those three depending on what you most need considering the rest of your roster, and your own preference/play style. And class could make a difference for you also if you’re planning to use emblems on the new candidate.
In my honest opinion, if it was me, and without any other knowledge of your roster I would focus on Heimdall and then Ratatoskr.
I am not really a fan of duplicates when you have other good heroes.
Whichever one you choose, good luck