The servers have now closed, thus the Platinum is unobtainable if you didn't get the online trophies before that happened.
Overview:
-Estimated Platinum difficulty: 7/10 (Platinum Difficulty Rating)
-Offline Trophies: 34 (29, 2, 2, 1)
-Online Trophies: 17 (13, 3, 1) - Unobtainable
-Approximate amount of time to Platinum: 120+ hours (Estimated Time to Platinum)
-Minimum number of playthroughs needed: 44 in Arcade at the minimum
-Number of missable Trophies: None
-Glitched Trophies: None
-Do cheat codes disable Trophies? No cheats
-Does difficulty affect Trophies? No
Walkthrough:
STEP 1: Offline Trophies
Get used to the mechanics of the game and focus on character-specific KO trophies and ones for counter-attacks or completing Arcade mode in various times. Many of these you will get without really trying for them. Also start working on Perfect Fighter by keeping track of your fight progress with and against each fighter (see trophy for more details). Overall you have to do a minimum of 44 playthroughs (roughly 2 for each character) for this step.
STEP 2: Online Trophies - Unobtainable due to server closure
In order to get all the online trophies you will need to play 1400 matches and win 100 matches in Arcade mode. This is where the bulk of your platinum time will be spent. I highly recommend finding a boosting partner in the Boosting Thread, or else it's going to take you forever. Although even with a boosting partner it will take some considerable time. Good news is that you should get the other online trophies along the way.
[PST Would Like to Thank Vyrastas for this Roadmap]