I can see where you're coming from, but I don't think incidental AOE damage outweighs the DPS saved from no DPS getting pinned at all. Particularly if you're in a PUG, no pins on a non-tank can make this fight go a lot smoother.
The problem is that you only get the no-pin when the people on the rail all know what they're doing. Most RDPS and healers, especially in PuGs, get pretty oblivious concerning enemies that they are not target and move out of their direct line of sight (which is what happens with the untauntables when you're on the rail). The rail-drop strat works great for coordinated guild groups that don't really need the extra help, but, for most pugs, they'll just end up screwing it up because they weren't paying attention. It's a risk/reward thing: you're risking the group splitting up and lowering tangential AoE on the off chance that the people on the rail will actually pay attention and drop before they get pinned. A vast majority of the time the risk outweighs the rewards when you're dealing with PuGs.
As to the incidental AoE, you'd be surprised how much additional damage you end up getting "for free" from it: all Smugglers should be dropping Flyby even on a single target but it's friggin' amazing with 3 or more, Focus spec Sents and Guards do a lot more damage when there are 3 targets stacked up, all of the tanks will do a lot more damage when the group is stacked up (Guardians with Guardian Slash and Sweep, VGs with HiB and Pulse Cannon, Shadows with Slow Time and FB), etc. You'd be surprised with exactly how much incidental AoE is in the game.