Last night I got 4th place in a 40-man tournament (again)
Are you P. Gorath?
After d1 hits you're at +9, so if you go for a 3 it's only 6 frames and shouldn't be interrupted(if you do trade it's probably with a poke which means you did more damage and should be left with a small frame advantage).
If they know you're going for that after a d1 they can back dash, but if d1 again instead it'll catch them(and they won't be blocking low so you'll be +9 again) or a b1 can catch a lot of characters if they back dash and should be mostly safe if they decide to do something else.
Not related to 3d2, but you're also guaranteed a 22 after d1 hits. You can link 22 on block into GS or d4. They can poke out between the 22 and d4, but if they poke and you linked into GS they can't get out(you should be doing this same mix up off d1). If they block the d4 you're at +15 and can jump in or do a b1 check or something.
I land most of my 3d2's after jump in attacks though. Ji2 obviously, but I get them off of ji1 a lot too. The range on ji1 is pretty ridiculous and a lot of the time you'll catch opponents who think they're out of range. It's also really fast and recovers quickly, it'll often catch opponents who think they're going to punish a whiffed jump or something. At the very max range of ji1 a 3d2 follow up will whiff(you can combo with b1~d4 at that range), but at most ranges you can combo into 3d2. If they block the ji1 I think they can poke out before the 3, but if you're spacing it right they're usually thinking about other things and won't get that poke out, and if they are poking out you can use 22 instead which is too fast to poke out of.
I also land 3d2 a lot in the corner. Either punishing wake ups or because they're too distracted by all your other options. Ares does work in the corner. There are some match ups where my entire game plan basically is to get them in the corner