Thermal detonators are almost good as is, other than being unable to be cleansed and some lackluster TD moves (I'm looking at you nute gunray) they are fine. You don't complain about damage over time not doing enough damage even though a single TD is turn for turn better than a couple of DoTs. The problem with Detonators aren't the detonators themselves, it's the characters they're given to.
Other then zam and jaws scavenger every TD character just tosses them and that's it. It's like if Vader just places a few DoTs and that was it, no culling blade, no reapplying, nothing and for a while that's why Vader was useless until palpatine and his zeta came along. Greedo for example has a small chance to gain a small amount of TM from using it. So yeah, TDs suck if you don't switch up your team for them, same as how a damage over time team would suck without Vader or boba fett to cash in on everything.