That's a huge stretch of logic. Complexity in encounters is an entirely different beast from complexity in gameplay. Encounter mechanics affect everyone and depending on how they're presented can still be fun while still not really directly affecting gameplay. Even if you don't like a specific encounter mechanic, you only see it in one spot in the game and move on. Gameplay complexity is a lot trickier, since you're stuck with it forever unlike mechanics in an encounter that may be unfavorable to your job. That and you HAVE to be the type of person that likes that sort of thing. If you aren't, you're SOL.
This is a flawed premise. You don't have the "option" of not hitting positionals because your damage is balanced around them. The only way such an option would exist would be for the DPS discrepancy between a DRG not hitting positionals and a DRG hitting positionals being something like 5%. And if that were the case you'd have people complaining that they don't feel recognized and special enough for hitting positionals or something like that.It's only complex as you allow it to be. If you don't want to hit positionals, then don't. If you want to be high end damage contributor, then you'll hit them. It's not complexity for complexity's sake, it's complexity to do high-end damage which mostly every job shares.
As far as BotD, its implementation is very much complexity for its own sake. I just think the fact they implemented it as a timer is tacky to say the least. The fact it only interacts with jumps and it only matters because of F&C/WT/Geirskogul makes it seem rather inelegant. It's a good concept but it would have been implemented better. Imagine if BotD had been implemented as a sort of super meter that filled up when you combo'd attacks, with F&C and WT as simply closers to Full Thrust and Chaos Thrust, respectively (thus not requiring BotD). Once the meter fills up, all actions performed (weapon skills, damage abilities like jump, off-GCD abilities and buffs like Spirit Surge) would drain on the meter with Geirskogul consuming the most out of all skills until the meter bottoms out (drained by actions rather than over time). In exchange, BotD mode would increase jump potencies by 15% and damage dealt by weapon skills by 5% (these numbers are placeholders).
On the side of benefits, you wouldn't have to worry about BotD dropping during phase transitions. You'd also set up future skills that could share a cooldown with Geirskogul with their own effects (maybe a single-target ultra jump that you'd gain during 4.0). DRG would still stand out as the only melee job with 4-step combos. Lastly, the RNG guessing game (which was not something everyone was going to like) wouldn't be there, and instead would be replaced by a rigid rotation while in BotD mode. Not sure if that would be better than what you have here, though.