http://compendium.ddo.com/wiki/Class:Ranger (go to the bottom and look up level 1-6 granted abilities. (TWF (level 2), and ITWF (Level 6), Many shot (level 6), Bow str (level 1), diehard (level 3) (this means you don't die from incap). Rams Might -Your hands increase in size, granting a +2 size bonus to Strength and damage. resist energy, are both good spells, for any solo toon.
6 ranger is never for spells (they are a bonus), Its for free ITWF, and Many Shot. If your close enough to a mob, you can open up with manyshot (sneak attack works on ranged weapons), then 2weapon fight the mob. 1 wiz for free feet, i like extend (nightshield, protection from evil,Jump or expeditious retreat (and rams might (ranger))), max would work for healing. You wanted dex over str so you have to do weapon finese or else there is no point doing a high dex. Its not low dps, it will actually be pretty high dps, not barb dps, and not STR rogue DPS, but it will be behind just because your build restrictions. Anything max dex is going to be low DPS compared to a max str build. Thats because STR is damage. Dex is hit.
As a dex build, your going to have to use things to get sneak attacks when soloing. Blinding weapons come to mind. I would use light picks or rapiers on this build. Finessable weapons.
Halfling Guile 4 adds +8 damage, and +4 bluff.
Rogue sneak attack training 4 adds +12 to damage.
If you want to change haste to damage that adds +5, but speed gives more hits, which leads to more damage over time, in most cases.
For a dex based toon, this is going to give you the best damage possible, unless you go 20 rogue, 20 ranger, or not want maxed dex.
So if you want this to do more DPS, drop dex to 15 up str to 16, put all points in str, and do more dps. Then i would tell you to go rogue 13, monk 6, fighter 1.
The build meets all your reqs, and it does everything you said for it to do. It will work in epics with traps.
P.S. where did you get the part of only taking ranger 6 for heals?