I was watching a streamer earlier today (ProfessorBroman) and I noticed a potentially great leveling area that may be Titan specific. He was around level 10-11 and I believe started a Titan specific quest. It was a dark map, you were given basically infinite super, and enemies were constantly spawning in clumps.
While I don't have the game yet, this may be worth someone looking into. If you were to spam your super to AoE all of the enemies down, then potentially die and/or reset on the last wave (a boss spawns), this could be exploited for very fast leveling. If you run into this quest, please give it a try and let others know. Hopefully it will be fairly obvious as you are leveling.