I gotta admit I'm guilty of not really moving the vocals around much in metal.
For rock stuff yeah I love automating everything, but in metal it's just hard to find the space. I normally spend all my time finding that 'ideal' pocket for everything, and it seems like every volume motion after that just takes it out of said pocket. Most of my automation in metal stuff is trying to get the drums in check, and getting the right low-velocity samples for fills, blasts etc. Then riding vocal and lead delays, verbs etc.
I only recently ran into the vocal automation problem on our first label release that we recently wrapped up. The vocalist, is, IMO, in the top 3 BEST vocalist for this genre (deathcore) and while I could absolutely STUN his 'high' vocals without the need for too much automation (since by then my meter was hardly moving, haha, but it sounded good!).
BUT, his lows and other aux vox actually sounded WORSE the more I compressed them (I was compressing about 3-6dB w/the CL1B on the way in, directly to tape for ALL vocals anyways) but, anything more than that, and for some reason, since his lows are so guttural, I lost all the aggression, detail and more importantly, CLARITY.
So here I am, with 13 songs to mix, and it hits me: I've got to automate ALL of the lower register vocals or else it sounds like shit.
I'll tell you what, it's the best, most clear I've ever gotten lows to sound. It's still angry as fuck but everything can be heard and I missed out on all the nasty artifacty stuff that can arise when dealing with extreme vocal styles.
I had never done as much automation as I did on the new King Conquer on anything prior, not even CLOSE. I'm riding the OH's, Rooms and (this is important) the bass GTR distortion channel on all the 'heavy' more intense parts.
I do the same as you though, Ermz. Get everything in the pocket, then go back through and listen for certain spots in the song that sound weird. It just so happened that EVERY part was sounding weird to me on this record.... haha...
Lot's of work, but well worth it.