This is more of a general online thing, but when I play my timing on most things is off. When I try to punish attacks and think I can land a hit in a combo, I whiff on an airdodge, spotdodge, or perfect shield. Part of it may be limitations of my characters (Falco and Robin aren't designed to be very aggressive) and lag, or my reactions are just slow. Does anybody know what I can work on to deal with this?
Honestly, a few things will throw your timing off. From minor lag (1-2 frames can mean all the difference.) to the simple fact you're playing a human opponent and not an AI (Which is a common thing that throws
my timing off, personally, since I play a lot against AI.).
It's not particularly useful advice, but playing online more will generally just naturally get you used to the slight delay in timing that both online (lag) and human players (Reaction times! -also, they can suffer from lag, too!) tend to have. I have the same problem - especially since I'm so prone to trying for perfect shields into punishes - so I understand the frustration completely.
Another minor thing that a lot of people also seem to never consider is nerves. Which, while it sounds silly, is also potentially the case since it's a rather serious (or at the least, hostile) fighting environment for most of online. It can throw off your game a lot, so if you feel like you're doing bad, take a breather and ease up before getting back into it. I know it's not exactly gonna be anything like the tournament nerves high skill players experience or anything, but playing fighting games against real people still gets you pumped like no other game does in my experience. Haha.
As for characters, well, I think characters without simple/powerful conversions or combos suffer most from this kind of thing, especially since characters with easy combos can be muscle-memoried to victory even in high lag (Robin is actually pretty okay for this IMO BC of Arcfire/thunder and D-throw combos and mix-ups being harder to react to and get out of, the big downside is that Robin is super slow so movement can be even more choppy.).
Greninja is probably
the biggest offender of suffering from dropping frames, whereas Bowser (Mmmm, up throw combos.) probably benefits most from opponents dropping frames while not suffering too much himself. Basically any character who has to play down to the frame and make specific split-second input decisions will have problems, and I think this sometimes has a
lot to do with the state of who wins and doesn't online. But that's just me.
TL;DR: Get used to the natural timings of your character so you have to rely less on laggy reaction times (everything is gonna feel like a monumental read otherwise), play online more to get used to general input delay, and if you're getting freaked about playing against other people then chill out a little and maybe take a break. If all else fails and the game is laggy as all hell for you, play Bowser and ride the muscle-memory U-throw combo train to wins-ville. :'v Ayy.