2-4 frames of animations is a whole world in fighting games, shooting games not so much due to how the games are processed, and lag compensation, rollbacks, etc...
before you post about anything i used to play starcraft and shooters like counter strike and quake exclusively before blazblue
in any case, fps != fgs so comparing the two is like comparing apples to oranges
online IS a good way to get better, and i think is the right thing for the OP considering how he prioritizes bb and his circumstances, but offline is a whole world of difference due to one frame links, attack startup, tech times, etc. etc.
if you CAN play offline, and are willing to sacrifice travel time/fees, by all means go for it, as it is superior to online, but online is decent if you have a solid connection, and a good way to learn even with some lag.
in completely competetive situations however, online is pretty much shit for fighting games.
edit: also ggs to cake on thread derail SO hard. lol