The chain time isn't an issue solo save for healers or tanks, because of low DPS. You won't deplete a camp fast enough to need any longer time, and you usually kill them about the same time your potion regen buff takes. You might need it more in parties because you can burn through mobs faster, and chains reset on different mobs. The issue is that chaining in general is bad exp, especially solo; you'd have to grind like 12-15 chain 30s solo at around 10 or so to level, which is hundreds of mobs. While exp in the FATE train in general actually isn't better in terms of time spent for it, do you really want to destroy your hands on doing an ffxiv rotation on 300+ mobs?