Most people avoid getting it themselves because it's very easy to get killed by little things, lag included (I myself died to the group with Healer's Boon at 1,100,000 exp). People who do manage to get their KoABD titles up the the maximum tier with the inclusion of EoTN will most likely be rewarded for it when transferring the title via the hall of Monuments into Guild Wars 2. I'm pretty sure there isn't a plethora of titles for no reason at all.
See above comment on benefit of titles that don't give a bonus.
Factions has the addition of the Assassin and Ritualist, while both aren't the best in PvE, they're pretty much a staple in the PvP aspect of the game. In Factions you'd also gain the ability to do Alliance Battles and gain exclusive PvE only skills from the Luxon/Kurzick factions, whichever you decide to pledge your alleigance to. Nightfall has the added benefit of Heroes, at least one of every profession, while you're only allowed three heroes in your party, they'll make the game alot easier.
Factions can be had for 30-40 bucks now and is definitely worthwhile simply because of the skills alone. And if you plan on doing PvP, you'll probably need skills from the Assassin/Ritualist tree. [see HA- Rit Spike/AB- Solo sin.]
Wurms are only in a very small portion of the game and i wouldn't base a purchase of the game off that, but the Heroes.