"More brutal"? How could becoming a villain again make him more brutal than he already is and always has been? This is a guy who ripped a mercenary's arm off and beat him to death with it a few issues back, once nuked a small part of Gotham just to demolish one single building, used a Mr. Freeze gun to torture a dude and cut his hand off, and massacred dozens of Ra's Al Ghul's soldiers in his one-man war to eliminate all of the Lazarus pits on Earth. Not to mention the carnage he made in Skartaris.
And those are all things he did after giving up being an outright supervillain.
Brutality has never been an area where Bane has been lacking, regardless of shifting moralities. Perhaps we'll see an increase in the frequency that those brutalities occur, but it's hard to say that that would make those actions more brutal. They'd just happen more often.
Also, just judging by the solicits, it seems that he's going to go back on venom because of this crisis of faith or whatever after realizing that the morality of giving up the drug has no bearing on him going to Hell or not. Now, that could be seven different kinds of inaccurate, both on my part for possibly reading too much into that brief synopsis or the solicitation itself, but I'll be scratching my head pretty hard if it turns out to be true. The use of venom being right or wrong had nothing at all to do with his kicking of the habit. He gave it up because a) he didn't need it, as the drug never made its user that much stronger than they already are (he and Batman beat up an entire gang hopped up on the stuff with their bare hands) and he was already a mountain of muscle, and b) depending on it was a crutch and a massive weakness that Bane couldn't afford. Regardless of the morality of it, giving up venom was a win-win situation for him, especially since his mind also wasn't clouded by chemicals any more.
Now, maybe the question of the immorality of using venom will have nothing to do with why he'll start taking the drug again, so my critique above will be entirely moot, which I hope it will be.