Using the skills when you don't need to isn't bad per se, though you might be a sad necromancer when you do actually need to remove a condition (like confusion) and the skill is on cooldown.
As something of a side note, I think that you might feel like you're a better player if you weren't just mashing buttons. Of course if you're on your own, mash away to your heart's content. It just sounds like you think skill is going to be a significant factor when playing with others, and that sounds like it's not much fun.
That's the way they designed the game. In lots of areas.Why is there seemingly so little in the game that teaches a player these game fundamentals?
How do I know if I'm close enough to use a skill? What do the numbers on these skills mean (referring to activation/recharge etc., not obvious things like listed damage)? How can I tell if I'm still in combat with something? Why am I slower when I'm fighting something? How far can I fall without taking damage or dying?
I could go on, but the point is that not everything in the game is explicit. Lots of things aren't even on the wiki yet. Some things I think are by design (ArenaNet doesn't intend to tell you the changes to the UI when you're in combat, you just end up figuring it out yourself or hear someone else mention the differences). Some things I think are simply oversights or things that I expect to be cleared up on the wiki... eventually (see: aforementioned traits).
Signet of Rage has a 60 second cooldown with thirty seconds of active time. It's pretty insane. But that's the fastest elite I could find on the wiki.
I do agree about comparing elites using the up times, though. And even the longest ones I could find were still on the order of four minutes, which isn't a particularly long recharge (I've had champion fights last long enough to use the asura golems twice even though they're on a three minute recharge).