Yup - each battler (monster or hero) has a roll of 11 (eleven) animations with 8 frames each, and map characters got 128x64 pixels in 8 animated frames on maps. I even go to lenghts of special magic casting animations, where each hero has his own magic animation (20 frames of the character making thunders, glows and etc). That big rat alone has a spriteset of 1600x2200 pixels, and any tileset isn't smaller than 256 x 6144 (and still lacks space for more stuff).
The speed isn't so slow that you can't play, but i'm worried about the future - if a dozen more tilesets of this size will decrease speed, depending of how RMXP work with graphics.
The tradeoff is SPEED... both in production and realtime animations. The big dissapointment in RMXP is the fact that it doesn't shows AVI animations, or my cutscenes would get niecer and easier to create.
My original goal on the maps is to get the same result as the maps from Baldurs Gate2 or those new 2D anime online games. Unfortunately, the tileset for those results would get about 256x 12288, probably more. I doubt RMXP would support that kind of bitmap... i should try it any day, anyway.