Hmm.. I might be doing something wrong then? I redownloaded the link but they're still the same size 64x64 which on paper IS supposed to work.. But when importing them into RPGMV they're so small, (Basically the size of a small stone in game I would say) and stretching them out in photoshop to a bigger size makes them lose their quality by a lot. I'm really lost on how the default asset images in RPGMV range from characters at 161x76 all the way to 511x 437 for dimensions. I also picked up your tileset bundle and that one I had hardly any issues getting to import into RPGMV, I don't know why the battlers are being hard to import properly :/
Unless we are talking about a different pack? The one I got was the "Raven Fantasy Battlers - Full Collection" which had battler set 1-4 with the battler heros set as well. Most of them have the variants of "Time Fantasy" too, with and without outlines.
I'm glad to know that they should work in RPGMakerMV though, was nervous at first that I got something that wasn't compatible with that engine lol, I'm thinking it's probably a step or two that I'm missing here, this is my first pack I've imported lol