Name 1 other class that only has 1 viable build. It's only Sunsingers.

Bladedancer, Gunslinger, and Sunbreaker The reason they appear to be better is they are slaying subclasses meant to kill. Sunsinger is a support subclass. The simple fact is there are a lot of buffs needed for a lot of different things.

False. Bladedancers, Gunslingers, and Sunbreakers have more than one viable build, and plenty of other options in their tree that are useful. Bladedancers can run an invisibility build if they want, for example. Or, for slide shotgun, they can use Fleetfooted. Gunslingers have different options which can make them more effective in different game modes. For example, you can reduce GG cooldown for 3s or Combustion for 6s. Sunbreakers have crazy options. Longer hammer duration, suncharge, sunspots. All these builds are useful. Sunsingers literally have one viable tree because other options are useless. For example, killing an enemy with Scorch drops an orb. Hitting an enemy with scorch knocks them back (doesn't work). Killing an enemy causes an explosion (Sunbreakers can cause an explosion on hit). Too many useless perks.

Almost all of those perks listed for other subclasses are just as useless. Invisibility isn't hard to notice or deal with at all. Explosive Pyre is a better Combustion and no Sunbreaker likes it. There's no perk to increase the duration of HoS. Sunspots? Really? The tiny, stationary flame that is so easy to spot and does so little damage? Right, moving on. Oh and I see you referred to Thermal Vent. That perk is bugged and costs Sunbreakers their melee. It's worthless.

No I don't think so. As a top 1% player that uses a variety of builds for those classes based on game type and # of players, I think you should do some research on those classes and find that other builds are just as viable.