Are you aware that Kaiten did cost 20 Kenki? Are you sure that losing 180/200/240/280 is meaningful choice? It's not really a choice, it's damage control, you might deal more damage if you just clipped it. Even if you wanted to call it a meaningful choice, it's not normal to struggle with double weaving at 2.40+, you would need to have more than 100ms ping to have that problems. So the "choice" comes not from job design, but from terrible server infrastructure.
Arguing about double weaving seems pretty off, SAM also needs to double weave every now and then with Third Eye (burst phase has 15 GCDs with 10-13 oGCDs, so if there's raidwide in burst, you will very likely need to double weave), and sometimes when you didn't keep track of your resources, you need to use Shoha so you won't overwrite meditation stack. Because typical slow SAM has 2.14-2.15 GCD, while GNB has regular 2.40+, it makes SAM more prone to fucking up double weaves. You used to need to always have 1 free weave spot before Iaijutsu for Kaiten, and you even needed to make sure you have 20 Kenki, which is already more involved than just pressing continuation after every Gnashing Fang skill.
Because Kaiten did cost 20 Kaiten, and had strict place in your rotation (just like Gnashing Fang/Continuation), you were supposed to use it (just like Gnashing Fang/Continuation), if you didn't, you simply lost potency (just like Gnashing Fang/Continuation) and it even had some improvisation and choice (just like Gnashing Fang/Continuation) - if you had only 10/15 Kenki, you could delay Midare by 1-2 GCD and build that last 5/10 Kenki without overwriting Sen.
