I returned after 4 years absence and wholly molly mate, the game IS HUGE !!!!! SO much has changed and there is SO much more to do.
I had 4 level 50 toons but I actually started all over just to refresh myself with the game as so much has changed. There is a lot to catch up on and even more coming ... DRAGONS and Necros! So yea, this is a great time to come back and enjoy the game.
Personally I took advantage of the eso character boost so as not to waste a lot of time searching and clarifying the whole situation. It also gave me the opportunity to raise my level of play. There are many experienced players in the game.