In a nutshell: yes, it is perfectly viable. Due to the lack of long-range long-duration crowd control, and the mounts, you should be able to dodge zergs and groups just as well as you could in Dark Age of Camelot for the most part. With the rapid healing rate after about 25 seconds of being out of combat, you also won’t have to worry about winning a fight, then having no health left a minute later when you encounter your next one when playing a melee type or a class without a healing spell. Additionally, with the higher Time To Kill (TTK) in WAR, you’re not going to die in a split-second to a caster that happens to see you as a melee class, or a caster who gets caught unaware by a melee class, though the latter situation would be harder to cope with.
Mounts provide a 50% boost to movement speed and take three seconds to summon. While most coordinated groups will likely run with them, that places you on even footing as far as speed goes, and better-than-even if they’re already engaged in a fight as you’re passing by. Due to damage knocking people off their mounts much of the time when hit, people won’t be mounting during fights unless they can get a good distance to try summoning and running. This will afford you as a soloer the ability to join in on a zerg’s fight, and if things are going south, run back into the zerg, summon your mount and run. It also opens up good hit-and-run tactics for interfering with group-on-group fights or smaller, especially as a ranged class that could go to a high vantage point, attack several times, mount up, and get out of the area before anyone can really reach you or react to your presence.
Uncoordinated groups and PUGs (Pick-Up Groups) likely won’t always run on mounts either, which means you would have a speed advantage over them. By being mounted when soloing, you’ll have the ability to make it not worth a group’s while to bother chasing you for a few minutes rather than just going and finding foes of more equal numbers who will want to engage them. There are many out-of-the-way areas and side paths in the zones as well that a normal group wouldn’t bother running through generally, but a soloer could use to his or her advantage readily to stay out of sight at the cost of a slightly longer travel time behind the enemy lines. With the extra paths likely also having soloers trying to catch up to their zerg, group, or seeking solo action also, you’ll generally find plenty of action on your own.