Roster priorities advice

Need some advice on where to spend my ISO. For the longest time my plan has been to max out and champ every single one of my 3*s before moving on to 4*s since I could use the LTs that the 3*s give, but recently I've been having some second thoughts on whether this is the way to go since my remaining 3*s are pretty much bottom tier guys.

My current roster situation:
8 3*s not champed (140: , 120: , 100: )

My one and only champed 4*:

And my other 4*s with enough covers to be worth leveling:
lvl229 5/5/3
lvl190 5/5/3
lvl160 5/3/5
lvl150 5/4/3
lvl140 5/4/4
lvl90 4/1/4 (this is the only 4* with less than 10 covers I've ever considered leveling)

And maybe worth mentioning, I also have a 5* (2/1/4) still untouched

The rest of my 4*s are all less than 10 covers, so the above 4*s are the only ones worth leveling to me. Given that only Deadpool (and maybe Charlie for PVE) can be considered top tier, should I leave my 4*s alone first and continue with my mission to max out all my remaining 3*s just for the LTs? Or should I even start to take a look at my Phoenix even though she isn't that evenly covered?