they're actually incredibly easy for the most part, there aren't exactly a bunch of 1-frame anythings in Dissidia
Tidus, Cloud, Zidane, Golbez, Bartz, WoL, Garland, Firion, Onion Knight, Sephiroth... pretty much every melee character has dodge cancel combos except I guess Squall and Jecht but Jecht has his own combo system and Squall has a bunch of links and he'd be even more broken if he had real dodge cancel combos instead of traps/resets. Terra/Bartz holy glitch combos are dodge cancel combos as well. Almost every character has EX cancel combos (maybe everybody but I don't remember if, say, CoD has 'em), there are lot of links in the game as well.
And then there are stupid spacing/stage specific combos like Tidus wall slam combos off that ground tackle-to-kick move or Ultimecia-on-Pandemonium ceiling combos.
And everybody has to dodge cancel melee stuff anyways if you don't want to get EX bursted.