Saying that Xuen does more damage than RJW is misleading, because you're applying no timescale to the claim. Both are appropriate for different purposes and needs. RJW actually provides more immediate damage between the two if used correctly in sequence with other abilities. (10 Stacks of TEB with Tiger Strikes and RSK debuff up + a sequence of RJW -> Chi Wave -> RSK -> FoF, or any variation thus, is
likely the most potent burst we have)
WW is a spec with a lot of options in terms of playstyle and personal choice. Often there is no right or wrong talent choice, but rather a right or wrong choice for your particular playstyle. Experiment.
Healing Elixirs is better than Dampen Harm against melee comps because it provides automatic self-healing with your typical brew usage patterns, making you an even less viable kill target. You've little use for Dampen Harm against such comps because...as "melee comps" would tend to imply, they don't tend to have enough magical damage going out to justify the talents usage. Elixirs honestly isn't even a bad talent against caster teams, it's just that Dampen Harm has an offensive use against such comps when used correctly as well.
WW is a spec you should expect to swap talents and glyphs around with a lot. It's very flexible. Use that to your advantage.