Luther is the hotness, to me. His 5 star is 10 hits, and has 2 possible effects. If his 6 star comes out anytime soon - he'll be the bees knees imo. Unranked for most tier lists.
Micheles 6 star is 18 hit with fire buffing and attack boost. Rank 11
Ice Fortress Oulo (Copra) - I have him, hes a beast. Ive seen different strategies on how to play him, but his six star form at max BB (23) crystals fills up every round to other. Gives your healer a good chance to pop out of guard and heal, then only take minimal damage if targeted. I only used him for questing though. Ranked 5
Bordebegia (Homusubi) - Awesome BB filler for your Mono Fire team. His BB hits 11 times and boosts spark. Ranked 7
Sky Mage Rashil - She "sounds" awesome. But I think the plan for healers in this game is to boost defensive capabilities. The whole point behind having a healer and a Utility. Never the less, you have a Healer, which it took me a.. month? I think, to get mine. #54
Rakshasa Lord Vishra seems to not stack up so well either. #73 11 hit with probable curse. I wouldnt say hes a bad unit though.
All in all, I think you got the start to make a great mono Fire team and quite a leg up for a questing team. Someone else might be able to help you more than I can. But I think you had some great f'n pulls.
Here is the Brave Frontier Unit Tier list that "I" like. Its updated all the time, so I think its better for that reason alone.Its all personal preference, though.