Currently I have a 1st life fairly high DPS Level 16 Elf Rogue Mechanic using a Great Crossbow. Feats currently are PBS, Rapid Reload, Quick Shot, Improved Crit, Improved Evasion, Skill Mastery, and Toughness x2.
Used Mechanic to power up the Great Bow, and I have vorpal great crossbow, which crits on 15-20 and vorpal crits on 19-20, tons of backstab dice and enough range that sneaking is usually irrelevant. Trapping abilities are so-so for most at-level dungeons with the mech skill boost available if needed. My typical great crossbow shot at this level is doing around 300 (200 + backstab dice) on first hit for backstab and 200 after that. I am thinking about adding in a few fighter levels to pick up Precise Shot and Precision.

The problem is, as I head towards 20 and look at Epic Destinies, I am not too impressed. Shadow Dancer seems to be the best ED, but only so-so for this build - nothing particularly attractive except Int bonuses and Ranged power. The other two EDs a rogue qualifies for are even less exciting. So I am thinking of reincarnating and changing two levels to grab six levels of something else so I can leverage another ED... but what? Also, after looking over some of the other ED's, I'm not sure the trade-off is worth losing the Level 18 and 20 Core Mechanic Enhancements.

As I haven't played too much Epic content, are there any suggestions on how to proceed for an Epic Noob?

Wait.. That's not sounding how I meant it.