I agree with most everything already stated. I use Dektol 1:2 most exclusively with MGIV Deluxe. Dev 90 sec, stop, fix for 3 min. If you're experiencing an issue with grain, you should suspect the paper replicating the grain which is already present in the negative. (via enlargement). I would say you're working with a very grainy negative. If you ever make a paper negative with MGIV and then develop in Dektol you will note this combination has no visible grain. Maybe there is though . . . under a microscope. I personally like grain, and also develop T-Max and Delta Pro in Dektol 1:2. Works for me.
"reciprocity seemed to be out the window" . . . good, I never found a use for it anyway. LOL!