Greensteel weapons are solid until level 24. At that point a tier 1 thunderforged weapon that costs 80 ingots does 4x weapon damage compared to 1.5x on a greensteel weapon. You can add 10-60 fire damage, 10-48 negative energy damage or first degree burns which adds stacks of vulnerability. Triple positive greensteel may still be better against undead, but other than that I don't think any greensteel weapon can compete with a tier 1 thunderforged weapon.
You can make khopeshes or any other weapon with thunderforged crafting.
Khopeshes of the drow weapon master may also be good at lower epic levels, but those are hard to get. There is also a nice khopesh you can make from the House C challenges, but I can't remember the name.
The ranger update will be this next release in a few weeks or so. Here are the tempest changes which you can test out on Lamannia now:
https://www.ddo.com/forums/showthrea...empest-Changes
If you are dual-wielding khopeshes it's unlikely that any pure ranger build will be beat 15 paladin / 5 ranger, but of course build the character the way you want to. 15 Paladin gives you holy sword which gives your khopeshes +1 critical range + 1 critical damage. You also get 10% doublestrike from zeal and of course you get divine might which lets you add your charisma modifier to strength and with all the gear options, this is at least 15 even if you dump charisma at level 28. You also get great saves + great defenses (defense stance from sacred defender with no downside).
the last few cores in tempest look good, but basically going pure 20 ranger means you are trading the last 4 cores for everything paladin 15 gives. you can still go tier 5 in tempest with 5 levels of ranger - the only restriction is you only have access to the first 2 cores and have to take greater two weapon fighting AFTER you take the 5 ranger levels. It will be a fun build.
If you want an evasion/dodge character 20 ranger tempest is very compelling, but less dps than a 15 paladin / 5 ranger.