A few pieces of advice:
1) If you intend to stick with this game, re-rolling for an S or SS character will do you well. An SS mage is never a bad thing. Late game, they murder everything.
2) There has never been a "god fest" sort of thing. Early on, rolling for better characters is totally normal. As you make progress and fill out your roster, it's not uncommon to spend energy on stamina to farm Coin Creeps on weekends. There are two "hatchers" - a coin and an energy. Coin nets you a shit ton of monsters, but it can also land you two SS characters. To my knowledge, they aren't incredible, but they aren't terrible. The second is an energy hatcher (like the standard magic stone pulls in PAD). This is where you get your goodies.
3) Bahl is pretty good. I don't know much about Ra'prow, but Ba'gunar is fine. I have had great success with Korin so far, but I also wasn't doing the T2/T3 arena event stuff when it was around. Grace is often talked about as being awesome...I think the -20% defense skill has something to do with it?
4) For progression, take advantage of metal zones when they pop up. Also take advantage of the new "distribute XP to lower level members" to skew XP distribution. Once you hit chapter 6, mission 6-8 can be farmed for metal tickets. NEVER spend them on anything but Metal Zone 3+ (MZ4 and 5 come around during events). Once you can get job 2/3 on a character, make sure you at least take them to 35 on the previous job. Skill slots + new skills = good.
There's a lot more that can be said, but the biggest thing you need to consider is if you intend to stick with the game or not. Grace may be your ticket to higher end content - some of the more experienced players will be able to comment on that. It may mean rerolling won't be worth your time.