Levels have increased, gear has increased.
Slow mitigation is omnipresent in everything after GoD.
In the 44-60 game, not all that much has changed in terms of gameplay. Pre Velious zones are still the best to level in IMO, mobs have a lot fewer HP and do a lot less damage. Taking newly available gear into old zones makes you own them hardcore, and it's fun
So much is buyable in the bazaar now: Try to get your old guild leader to lend you 100K, you will be astonished what you can get with it.
At level 55 you should buy the energaic stuff (required 55, reccomended 60) for the visible armour slots - it's really awesome and probably dirt cheep (1000pp per slot generally). Buy some of the pop molds for the clicky effects.
Buy player made jewellry for fingers, ears, wrists, neck and face. goto
http://www.kyros.info/Tradeskills/JC-Calc/ to see what you can get.
Buy 8 each of the cut Peridot , Emerald, and Taafetite gems from the bazaar. In the 40;'s buy trio platinum settings and put the gems in. In the 50's buy trio velium settings and move the gems across, trio palladium for the 60's and trio dwerium for the 70's. The dropped items for those slots are totally and utterly outclassed by player made stuff. At about 5-10K per slot you won't need to bother re-gearing those slots for a long long time.
That pretty much leaves you primary, secondary, range, ammo, charm and belt slots to fill.
Spells: most spells < 70 can be player made. I'd simply buy them in the bazaar rather than hunt for them.
Enjoy the journey levelling up.
Recently bonus XP was put in for people with few AA's (if you have less than 759) to help people catch up on AA's. I'd say find a spot in the 50-70 range where you feel comfortable and can do a bunch of AA's and stay there for a while.
Mostly though, make sure you enjoy the levelling. Stay in zones that are fun for you until you want to go somewhered else. If people invite you to go somewhere do it, variety is the spice of life after all.