As A.bakker noted, AoE plants are almost always better in Endless, and Fume Shrooms > Gatling Peas.
Single-target damage is very insufficient late game for dealing with the huge numbers of zombies, and AoE plants then will deal overall much more damage, even accounting for the small AoE given by Torchwoods. For this reason, a Melon-pult is considerably more effective than a Gaitling Plant for dealing damage further down the lane, with a Winter Melon being even better because of the frost effect.
The only single-target damaging plant I would recommend is Cattail. This is mostly because they pop Balloon Zombies, but also because they can attack anywhere on the map, specifically covering for thrown Imps and Diggers, and dealing enough damage (equal to a Repeater) to deal with their low HP. Some successful strategies have none, some have one or a few, very few have large numbers (or the entire pool of Cattails), though at least one is required if you don't want to use Blovers or explosives.
Fumeshrooms can cover Diggers and Imps generally more efficiently if placed near the back due to their higher damage, AoE, and less lag (Cattails projectiles have a relatively delay in reaching the target compared to other plants). They are more useful in builds without Cob-Cannons, as there is a greater reliance on immediate AoE damage.