I finally finished Hyrule Warriors' TP map today, and it was a LOT easier than I thought it was going to be. Literally the only two A ranks I'm still missing are the ones from the upper left corner I mentioned in a previous post. THIS was the hardest it ever got. Are you serious? Whatever happened to the "you NEED everyone to be AT LEAST level 120 to even stand a chance" everyone was saying (some people going as far as throwing the 150 figure around)? As of this writing Link and Sheik are the only ones who've reached level 120, and no one else is higher than 110. It's not like I'm an amazing player or anything, I just found out yesterday that you could delay Ganondorf's combos to make his C1 bar charge faster, making said C1 virtually spammable. I figured out a very basic thing near the end of the game*! So yeah, it's not down to me being so great.
On the other hand, I tried a few missions in the MM map I couldn't A-rank on my first go, and they're much, MUCH harder than anything the TP map threw at me. So if anything deserves that "you can't 100% it without loads of grinding" reputation (Challenge Mode notwithstanding), it's MM, not TP.
*In my defense, it wasn't that useful before the MM pack came out, because back then the bar charged so slowly and there was no invincibility on the fully-charged C1, so it wasn't worth cheesing.