Maybe these :

https://www.gog.com/game/etherlords
https://www.gog.com/game/etherlords_2

I just posted a longerish post about ESO (Elder Scrolls Online), but GOG ate my post, so here's the short version:

All four classes from the base game have DoTs and Templars, for example, have a lot of AOE DoTs.

Edit: After maxing out an active skill/ability (it doesn't take long) you can pick a morph from 2 different morphs, which give it additional bonuses or effects. Every class has three unique class skill lines, in addition to skill lines available to everyone else.

Check out UESP or ESO-Skillbook, Fextralife is outdated at the moment.

Some games have strategies of this sort that do not involve damage over time. For example:

* SaGa 1: Have your characters defend with shields until the enemy runs out of attacks, at which point it will run away. IF this happes in a non-random encounter (like a boss fight), the enemy will instead die outright. This does not work on the final boss, and there are a couple of other instances where it won't work (because the enemy has an attack with infinite uses), but it turns out to work well against a certain major boss who can give many parties (including solos) trouble. The drawback is that even shields have finite durability; each shield only gets 50 uses before it's gone, and if you have no attacks left, you can't do anything except try to run (though you are not forced to, unlike enemies). Also, this does not work in SaGa 2, as enemies don't have finite attacks there.

* Final Fantasy 5: Equip a character with a weapon that randomly casts a reflectable attack spell and a Reflect Ring, then deliberately get the character affected with Zombie (the hardest part of this setup). Then, during a fight you can't run from, have somebody else hide. A Zombie character can't be killed, and the hidden character will prevent game over, allowing the enemy to be slowly killed by reflected spells. (Note that this won't work on the superbosses; Omega has an attack that removes the character from the fight (that I believe Zombie doesn't prevent, but I'm not actually sure), while it's possible to run from Shinryu, and the hidden character will result in the party running away (I think).) There may also be boss-specific strategies (like against a certain boss that only uses reflectable spells).

Edit: Neither game is on GOG, however, although both games can easily be emulated.

I noticed after going through my tabs that this is just a repost from a year ago, someone linked it in that very thread (I thought I had actually lost my response, when it was in the other one! :D)

https://www.gog.com/forum/general/damageovertime_weaponsabilities