The Tholians seem to be really advanced. In the Enterprise episode with the time ship, they wiped out a whole group of Suliban and crippled a Vulcan combat cruiser, and it didn't look like they were trying too hard.
They didn't use the web weapon but did use some sort of beam weapon, which quickly turned the Suliban into scrap. The LUG books mentioned that they use some sort of plasma weapon, and if they do live at extremely high temps (by most standards) a Tholian boarding party could pose an extreme risk to the ship. Imagine Tholian marines coming aboard in armored suits. If the suit is breached, the Tholian is a goner, but so are most carbon based lifeforms nearby. If plasma or some sort of high energy is a part of their physiology, coming into direct contact with Tholians is not a good thing. Maybe they're really made of nanites... who know's.
"Retreat?! Hell, we just got here!", annonymous American Marine, WWI
"Gravity is a harsh mistress....", The Tick