I played this build for a very long time. It is a very powerful dps build and you don't need to swap for melee weapon, just all ranged.

Repeater lack some burst dps, but manyshot compensate this, if you choose FotW ED. (remember to use manyshot wisely, because the -100% DS penalty also affect repeater)

The first T5 I played is 10% Doubleshot from Mechanic. It's plain and strong, increasing your dps very much.
The second T5 I played is Improved Precise Shot from DWS. Due to Precise Shot bug in the past, it gives you a net 50% dps increase almost all the time. But now it only worth in boss fight, and requires you to stand still. So I gave it up.
The third T5 I played is Slaying Arrow from AA. It's a huge AP waste if you want to get it. But Slaying Arrow worth the cost.(This require you to use FotW ED)

Other enhancement I suggest: Scroll/Wand Mastery from Mechanic, No Mercy from TAcrobat, Killer and Merciful Shot and Aimed Shot from DWS, Venomed Blade from Assassin, Leg Shot from Mechanic or DWS, core abilities from elf (which increase the PBS range and to hit) or halfling (which gives you some saves) enhancement. Choose them wisely

The only shortcoming of this build is Saves, so it requires you to have a good knowledge of how to fight in various situations.

I'm in my 3rgr3mnk TR loop. But I think I will go back to this build in the end.