I'm not sure the area effect aspect of combos matters much in CT, because the only time area effect matters is in regular battles, and you have no reason not to just mash Attack through pretty much all of those except for a few special cases. Also the few bosses that do have helpers or are multipart, you're going to have one attackable thing that's immune to magic/a certain element and another that isn't, rendering the area effect moot.
I'm also not sure I even bothered using triple techs. I mostly found that they made things harder because, while they do more damage, they also pretty much lock your party into doing the same thing for that round. Meaning you can't have a healer waiting around to case heal in case it becomes necessary. Which is something I even kind of encountered with double techs.
bizarre leveling system (almost would've worked had the lion's share of level based stat gains not require you to fight supplementary battles immediately after every boss fight with everybody)
You don't really need any of those stat boosts. It's not a particularly difficult game, and the stat boosts aren't particularly large.
guide dammit recruitment requirements
About half of the characters join you through the regular coarse of the game. Of the remaining half, I... think I only had issues figuring out what to do with Mojo, NeoFio, and Turnip.
'pretty good D&D spell casting knockoff in all cases save for this particular one' Elements system
the game failed to live up to fans expectations
I've seen enough aborted/semi-finished fan made CT sequels/romhacks to have come to the conclusion that most fans have pretty stupid expectations. Go look up the youtube videos for shit like Crimson Echoes or whatever that was. Most of the CT fans that complain about CC had their little pet theories and fanon, and this wasn't addressed by CC, they flipped a shit. Every time you see someone complaining that CC retconned CT or broke established canon? No. CC doesn't retcon anything.
Fans of any game have stupid expectations, though, and actually listening to them is a pretty bad idea. The guy that runs Spiderweb Software has a good article/blog post on this somewhere. So did the guys that did the more puristy remake of Privateer in Vegastrike.
Eh, CT was pretty much designed around the 'the developers want you to use this particular attack now' theory in the same way that FFXIII was designed (except that CT lets you power your way through without using the particular strategy at the expense of using more resources instead of punching you in the dick and making you do it again until you get it right like FFXIII does). Dual Techs and Triple Techs fall under the same idea. You have instances like the Desert in the Middle Ages where attempting it early will kick your ass and the boss counters everything you do with upping it's defense save for hitting it with water magic; slamming it with a Dual Tech then will save you time instead of having to debuff for both attackers separately.
Triple Techs are only really useful in moments where a boss whips out its final and most brutal attack pattern and the fight devolves into a damage race. Nuking it with a well timed Triple Tech can expedite the fight's end.
As for my comment on CC's Elements system. It really is a somewhat more streamlined version of Dungeons and Dragons magic system where you assign a number of spells to use per day (or in CC's case Elements per battle) from a collection of spells with the spells separated by spell level and with certain feats can be empowered or sped up in casting (or in CC's case Elements are also broken up by level and adjusting Elements to higher levels empower them or to lower levels to activate them quicker). It's a fine system in it's own right, but trying to manage such a system between 44 characters with differing shapes and sizes of Element Grids and with different innate elements was it's one fatal flaw.
As for CC's failing to live up to expectations; you got to admit bumping off CT's main cast off screen (save for Robo who gets to die onscreen (kinda)), not letting anyone visit even one familiar local, mostly squanders the dimensional plot gimmick, constantly bludgeons you over the head with environmental messages, and only getting around to the one plot point left hanging from the previous game at the end with out of nowhere walls of plot dump that basically boils down to two CT character's Xanatos Roulette of a clusterfuck of a 20 Xanatos Pileup kinda leaves most people scratching their head going "WTFH!?!?!".
The tl;dr is that I really need to spend less time writing these things. They're not even offering me anything insightful anymore.