chydis + basic units = 3 healer strat. +mehlis +valerie = your 2 mages. easily managed. also I should point out that I only mentioned Imelia + leeanne/bernard is needed in addition to backup lightning rods. if you're high level enough, they might not even die and lightning rod not even necessary. your dahlia + maribel pretty much replaces Imelia and Leeanne/bernard I mentioned.
also, not everybody has units like yours (my best valk is a kerry and that's because I joined before Bashira became tutorial summon) so not sure what your point was. my theory was based on relative new players who've been playing at least since Imelia's event (which is like, this month)