You did WvW, which is a completely different animal from sPvP. sPvP boosts you to 80, gives you exotic gear and unlocks all skills and traits and skill slots for you. The only grind in it is for epeen. I personally can't stand WvW, but greatly enjoy sPvP.
I had a very different experience while leveling. I consistently out-leveled my story missions when doing zone completions on my guardian. However, I also went out of my way for group events and gathering modes, both of which give a significant amount of experience.
Also, not to nitpick, but: your traits and utility skills do more to define your role than your weapons. Using engineer as an example, a rifle engi can be a bunker, power burst or support in sPvP. Which the engineer actually is depends on their traits and utilities (and amulet, but it's less defining). I typically play pistol/pistol engineer, which can be control or condi dps. The reason for P/P is that rifle has fewer conditions than pistols. Deep alchemy traits combined with elixir utility skills give group support and slipperiness. Deep invention traits and skills would make me tankier and more control-oriented (pistols have an aoe root and blind that helps with that). I could go on, but hopefully you get the idea: weapons are only one piece of what defines a build. That's really good, because engineers only have 4 options for weapons (not counting kits, which are also utility skills).