/click -- why?

[Ualaa]

One button spam is easier then spamming 6 buttons.
And with the proper comma's (delays), each is refreshed either as it expires or when the recast delay allows another cast.
Plus you can prioritize your spells, so you'll never attempt to Conflag without Immolate up (as an example).

[Khatovar]

Plus you can prioritize your spells, so you'll never attempt to Conflag without Immolate up (as an example).

This is probably the biggest as far as I'm concerned. A lot of "rotations" are not exactly spell rotations anymore. Certain spells have priority over others and /click allows us to make use of that without having to make massive, intricately timed cast sequences, which can start to cost us DPS if cooldowns and priority start to clash.