Maybe this is different on the PC, but on the PS3 I never had ANY issue seeing what mobs I would be facing and had ample time to switch my abilities if I wanted to (which I sometimes did).
I'm aware encounters aren't static. But my experience with the game isn't one where you're not able to change to a new build before engaging with a new type of mobs, in new populations. The only time I ever had surprises in encounters was when you head into one of those alcoves off a main hall that's kept really dark until you're in it.
And even then, you knew you'd want AoE skills going into those rooms.
The sum of that meant that this:
Encounters aren't static, you don't really know what affixes you'll get until you see the mobs, so you can't really plan for it beyond building a solid general build.
was completely false, even when ignoring the fact that the PS3 version lets you change abilities mid-battle.
It was never, never
wise for me to build a smart general build, because a general build was ALWAYS under-powered relative to the tailored build (unsurprisingly), and it was quite easy to jump into a tailored build. It was stupid to have more than one single target ability for general dungeoning, because you could quickly switch in more before engaging a pack that had named mobs. And then your boss battles had you jump into a dedicated kiting/ST/survivability build.
My choices never mattered. There was no permanence, no value to my decisions. They'd matter for a few seconds, and then I'd make a new build choice moments later that mattered for a few more seconds.
Having access to a tool that was perfect for every situation made the entire combat system feel incredibly boring to me. Sure, sometimes the endless destruction aspect is fun. But it will never be interesting enough to me to hold my attention.
And since I don't see any particular pros
if having the D3's access-to-everything system, at the actual player experience level, it really just sucks to me.