-1 quality sparring partner (understands the game, plays respectful when needed) -high quantity of matches played on a regular basis -communication pre/during/post match -healthy dose of training mode pre/post online sessions, to keep your muscle memory tuned to offline -respect for your opponent
If two non-scrubby players follow these small guide lines, they can definiteely use this game's online as a medium for development and improvement. Not as effecient as offline training sessions, but it definitely can be used effectively. Also, consistent connection is obvious something you'd benefit from. --- PSN: shakobe Putting mark busters in their place since 2009.
You can be good at it online, but the limits of how good you can be if you isolate yourself in an online environment is... well.
However, playing offline doesn't necessarily mean you get better either.
The main factor in getting good with any fighting game is that you play with a vast variety of people. Expose yourself to all the skill levels and game elements that different people use. This is why people of countries outside the US usually are having a big problem actually becoming a big name in MvC (because of the lack of exposure in the big stage) --- UMvC3: Felicia (A) / Amaterasu (B) / Strider (Y). Philippines' Felicia and Amaterasu representative. Offline PS2/PS3 pad player with weird configuration.
Never forget that Viscant primarily trained for Evo 2012 through online play, and the netcode was much worse then. --- My Ultimate Dormammu Guide: http://tinyurl.com/6mr4lhv My UMvC3 Team Building Guide: http://tinyurl.com/8x865ra
If you play online with a small handful of people that you have a decent ping with exclusively and agree that your matches are primarily for training purposes (meaning that you don't just run your primary teams up against each other for 2 hours a day, you actually agree to help each other practice defense, setups, tech chasing, etc. without concern for your W/L at the end of the day), then yes, you can train somewhat effectively online.
But never underestimate the physical/mental effects of simply being in the same room as people you're playing. Self consciousness, intimidation, lack of anonymity, etc. are all things that online sessions won't account for and won't help you get over.
Not criticizing TC, just offering perspective from my own experience. --- NP: Path of Exile, UMvC3, SFxT UMvC3 Lab: Doom/Storm/??? SFxT: Cody or Poison/Heihachi, Alisa/Guy