Tips for playing Dissidia:
1 - Pick a character not that you like, but that you're good with. I found Zidane's speed suited my hit-and-run style best at first, and he has a nice, sudden "POP!" HP attack that nearly always catches the AI offguard.
2 - Level your first main up like crazy, well ahead of everybody else so that you can gain a TON of Gil and buy all the equipment for all the OTHER characters before they level up. Half the time when this game is too hard, you're experiencing the power gap between your equipment and the CPU's. Equipment is the stupidest addendum to this game and mars what's otherwise a pretty darn good set of mechanics by putting level grinding between you and what's otherwise a fair fight, so muscle through with one character and use that character's riches to get around it for everybody else.
3 - The other half of the time you just don't have any good attacks and haven't developed a playstyle. That's a huge, huge part of this game, and one person's Zidane can be WILDLY different from another's depending on what abilities they equip. There's no other way around this but to continue playing, level up, and experiment.
4 - The OTHER other half the time your accessories are wrong. I'm not even sure what the combat multiplier DOES, but it seems like you have to find a balance between that and lumping just flat damage bonuses. This is another of those things that gets into building a playstyle, and you have to really think hard about what you do when you fight with any character. Also more grinding because you have to get those @(#!*$% Rosetta Stones to get new accessory slots. HA!
5 - Once you figure out all this stuff over the course of taking your main through story mode, adopt your real main and see if you can find a playstyle with them that you like.
6 - Story mode, story mode, story mode. Play it over, and over, and over again with the hero characters, because you get a disproportionately HUGE amount of EXP for those puny throw-away mooks between you and the real fights, and the first time you do it you will turn out underleveled almost no matter how many of them you choose to take out. Just keep re-doing it until you're level 50 or so and repeat with everybody else. By the time that's over, you have a crap-ton of gil and can actually afford to fight opponents at your own level for a while.
The game's not that hard, it's just grindriffic and has a HUGE dependence on customization and playstyle building. It's actually a fairly deep design, but with flaws in that--well, like I say--it depends on grinding when it really, really, REALLY just shouldn't.
Example: I've got a level 100 Sephiroth, but in order to get a fair fight out of someone I have to fight like a level 80-95 CPU in quick battle mode. You see, you can't actually buy most of the high-level equipment normally, and most of it depends on finding synthesis items that you never see either in quick play or story mode. Instead you have to find them in the battle coliseum, where you find treasure cards that contain these otherwise random and totally useless accessories, like "Humbaba's fang" and "wyvern horn." Elixers can be traded for almost any of them, and that's what you really try to farm in the coliseum. The coliseum itself has several courses which move in tiers corresponding to different level ranges, with the Lunar Whale course being the hardest and the one that you inevitably have to farm the most in order to get level 100 equipment, which'll take like fifteen Megalixers to synthesize. The level 80+ equipment all works like this, and you'll spend a long time farming elixers and crap to put together a weapon only to find out that you've long since surpassed the level of the weapon you've been trying to synth. You've spent hours of your life farming elixers for what is now sub-par equipment.
ON THE OTHER HAND...
The CPU at level 80+ on "normal" settings is just automatically HANDED equipment that matches its level. That's right, the barriers between you and equipment that's actually your level are nearly insurmountable monuments to tedium, but the CPU just waves it around like it's nothing. This applies to both its weapons AND its armor, so your weapon is not only sub-par, but it does less damage anyway for the same reason that they do way more damage to you.
Yeah. This game hates you.
