Lol. There used to be LFMs requiring a "potion buy in" to running Vod.
Yes such things seem silly now. But, sad fact they were a complete reality.
As someone who ran Sub T and Shroud on the regular with a lvl 16 (at the time cap) Cleric it could very well be a huge drain on resources. Just because some newer folks were not around for those times doesn't mean they didn't exist.
I do agree almost all raids have been called a potfest in their introduction, and were latter managed to be better. And through nearly every one I was playing some sort of Divine healing the raid. However, raids with SP drain have an overwhelming chance of you having to chug a few pots without consideration to how well your group is doing or how well you are hiding behind a rock. So yes, a lot of raids were potfests in the beginning and Yes SP Drain is about as stupid a mechanic as you have in this game.