Firstly welcome to GW2.
Secondly, don’t expect this to be the same as WoW. There are many similarities but there are far more differences.
I played WoW from just before TBC came out and came to GW2 at launch, even having played GW before WoW it was a steep learning curve. My best suggestion is to try each class and see if you like it. Also take it slow, in WoW a lot of content is aimed at max level characters in GW2 the game starts at level 1 and leveling is a major part of it. I see a lot of threads from people who have rushed to get to level 80 and then don’t feel they have anything to do.
As far as classes go, one thing you will notice is that you have far less skill to chose from, each weapon has a set of 5 skills and once they have all opened up you don’t gain any more weapon skills. Utility skills are where the variety is, but you only have 3 of those active at any one time and one elite skill. The art is to learn when to use the skill, just because something is off cooldown, doesn’t mean you use it straight away, timing is important.
I mained both rogue and hunter in WoW. Ranger and Hunter aren’t that different although Ranger does have good melee ability, something that the Hunter lost. Thieves are similar to Rogues but there is no permanent stealth ability, again it is a matter of timing. Necro and Warlock have similarities both are good at damage over time (conditions in GW2) and both have access to minions.
There are no specific healers or tanks in this game, every one can heal to an extent, and every one can tank but maintaining threat is far harder, one of the main skills to learn is to avoid damage, most importantly learn to use your dodge ability.
My best suggestion is to try different classes, and different weapon sets and most importanly have fun.
