Yes Shiraishi, I'm a fast typer.
Substitute takes away 1/4 HP of your MAX HP. If that number is 360, then your Substitute will have 90 HP. If you're at 200/360 HP, then Substitute, your Sub still has 90HP. However, it has its uses.
-Prevents a nasty OHKO move like Draco Meteor vs. Ninjask
-Prevents status conditions
-Allows Focus Punch to hit with little trouble.
-You still restore HP with Leftovers behind a Sub.
-Sub may be Baton Passed to another target, holding the same amount of HP as the original substitute has
Unfortunatly, if you're burned/poisoned already, you can't do much to stop it.
for Drifblim, if it can get Calm Mind, get it Will-O-Wisp. This will keep physical attackers at bay while you Calm Mind. Shadow Ball works just fine. Sub and Baton Pass obviously. If you really wanna take the risk, you can go Ominous Wind. You won't have as much damage but if that ability of Ominous kicks in... ouch. Major Baton Pass power! However, you won't need much speed. Def. and sp. def are keys, and obviously, HP.