Your biggest possible upgrade is weapon with higher dps. Aim for ~1200 dps. Crit dmg (native plus as a socket) should be in the package also. The increase of base weapon dmg would be a boost of n*10% to your overall dps.
If you are concerned with loh, I suggest putting it on ring (you can easilly get a ring with dex, 300-400loh and crit, such unities, which btw give you additional base dmg, cost ~2mil), maybe amulet (~800 loh, but don't forget other stats). LoH can be boosted by ias (as your dmg can be, too). Moreover, I would suggest using the most unpopular Hungering Arrows rune - Cinder Arrows. I found it to be not that worse than the popular ones, while providing you with 130% loh proc (compaired to ~60% proc of other HA runes).
However, if you are doing farming runs (on mp1, I hope), changing smoke screen to shadow power would diminish the need of loh or ls, for 15% ls is more than one could need. For ubers on high mp, however, smoke screen is still a must and loh is an extremely useful thing.
As for "getting rid of sentry", that thing is very useful on low mp farming runs - you just put it and run for other mobs, while the sentry produces xp killing white mobs. I'm also using it on ubers, though I'm not so sure on how optimal it is in this case.
As for skills, it'd try to get rid of these caltrops and stack CC on items. Then you could also change Custom Engineering to the 20% dps boost (Steady Aim) or the EHP increase in the form of Perfectionist.
And your CC is extremelly low, you could easily get at least 8% on quiver (talking cheap and not loosing stats) and several points on juvelery. I think, firstly I would buy a cheap quiver for similar stats to yours plus CC and (most importantly) a weapon with higher dps, sacrificing the loh. Then, concidering how much money you have left, I would search for rings (CC+loh, CC+CD, ias+...) and amulet.