My Arena Assault range during Earth season is 740-754 right now (lead Legendary Ike, Soren, Caeda, Titania) and 738-752 otherwise (lead Marth, Soren, Caeda, Titania), and it's definitely not fun to deal with all these dragon armors that might even have Svalinn Shield just to screw you over. I've got more than enough units to cover them for 7 rounds and my first team will never have trouble with them, but if I want to also maximize my blessing point boost then it's suddenly not so easy. I don't think I saw a single team without Legendary Robin, Legendary Tiki, either Myrrh, or Performing Azura.
Ideally there will be a bit of a drop-off in usage when it's not Earth season, but we're getting like 2 months straight with Water season now so you better hope that this month's legendary hero isn't another dragon. This is partly why I was convinced to start building Sheena anyway though, Slaying Hammer Sheena is an excellent answer to Legendary Tiki. In total I have 5 armor killer weapons with Caeda, Nephenee, Oscar, Micaiah, and Sheena (6 if Tobin counts but I haven't used him lately), and I have 4 dragon killer weapons with Marth, Masked Marth, Julia, and Legendary Tiki. Ike, Soren, and Titania can also handle both unit types within reason, but then throw in all the other units I need to field and there's a lot to account for. If this game would give me more Sorens I would actually be considering Watersweep over Windsweep on Sothe, and Watersweep Julia for that matter.