I think you're at the point where your success depends entirely on having attack buff + haste on the entire party. That's the easiest improvement you can make. Ramza is a god in this realm because Shout fulfills BOTH of these functions, but there are other options available to you. At the very least you want Hastega, if you can afford it, stick an attack buffer in there as well.
Your roaming warrior SB should be either Shout, Grimoire, or Stoneskin, and then remove all instances of that from your party. Make some friends with Ramzas!
One more thing: BSBs are really important since they essentially grant free abilities to your units. The single most restrictive aspect of this game is the number of ability slots you get. BSBs are game-changing because they essentially allow you to have 4 ability slots instead of just 2.
The rest of the advice is for even higher level (endgame) content, or if the above advice isn't enough.
I don't think Cloud needs a "Mog's Teachings" materia here, I usually reserve those for those with necessary buffs (Shout, Grimoire, Stoneskin come to mind). Using Mog's Teachings materia on DPS usually isn't totally worth it since it only affects the beginning of the fight, whereas a longer-lasting materia effect provides more damage over the course of the fight. Additionally, it's usually wise to save your DPS SBs for the last phases of the fight so you can zerg the boss down before he uses his most powerful skills on you.
Cloud could use either a sword attack materia or a SB charge materia. I also don't think you need two Dual Delay abilities for Cloud -- perhaps give him a Break ability?
What is Rinoa doing for you here? Having a single character ONLY doing DPS is limiting the overall potential of your party. IMO you should give her some kind of enfeebling / buffing ability in addition to a damaging ability. Also, maybe replacing her with a physical DPS would be good, since you should also be using a party-wide attack buff which doesn't affect magic users.
One last thing with Beatrix --- your sescond ability (I forget what it's called in global, in JP it's Zengiri, the AoE attack ability) can be replaced with something that gives Beatrix more utility, since usually you're not attacking multiple enemies at once in bosses. It's deadweight. If you're just fighting normal mobs, you shouldn't be using abilities either, besides healing when necessary.
My general philosophy at higher levels is that every character should be ABLE to contribute something besides raw damage. They should be flexible --- you know how terrible it is when your one dedicated healer doesn't have her charge yet after a huge AoE move.
As an example, I usually have my DPSes running some kind of break + soulsiphon and I alternate between the two every turn.
The rest is subjective, but I'll give you my personal strategy for clearing lv200 bosses:
Raw DPS / breaker / weakness exploiter (Bartz)
Raw DPS / breaker / weakness exploiter (Cloud)
Support / buffer / Full breaker (Ramza)
Healer 1 / Magic DPS (Selphie)
Healer 2 (Aeris)
Roaming Warrior: Stoneskin / Sentinel's Grimoire
I like this strat because each character has a somewhat unique role, but at the same time the entire operation doesn't fall apart if one person goes down (with the exception of Ramza). Additionally, in higher-tier battles, having two healers is a HUGE boon, even if one of them has medica, even at the expense of DPS.
This strat is able to clear almost every single challenge in the entirety of the JP version, barring the lv250 Nightmare battles and the Abyss dungeons obviously.