I have to recommend Nightfall to the serious GW gamers now. They've stuck it to us with an expansion that can't be ignored. Of course, an expansion a year is still cheaper than WoW's monthly fees.
Anyways, nightfall can't be sidestepped because of the introduction of heroes (henchmen whom you outfit with your choice of skills and weapons) and armor that accepts mods (Canthan and Tyrian armor doesn't take them, and they're not just handy for swapping builds as some mods appear to be entirely unique to this new armor system). Lvl cap is the same, so you wont be sub par without it, but it provides more 'edges' than Factions did.