As soon as you find a unit in the Ork codex with better long ranged anti-tank capacity and survivability, you let me know.
Personally, my lootas almost always perform to my satisfaction. As long as there are MCs or AV 12 or lower vehicles or other long-ranged targets of opportunity, they support an Ork horde army really well. They're not as necessary in a mechanized list since that army type can strike earlier.
They don't necessarily kill an amount of points equal to theirs, but they provide a much-needed service by killing transports, daemon princes, etc., that let the rest of the army perform better, and they do it on turn 1 from across the board, something that can't be said for any other Ork anti-tank except a kannon battery, which is even more vulnerable (and 36" is nowhere near as nice as 48".) 15 lootas in cover is fairly hard to budge with a horde breathing down your neck, mine almost never die or are even shot at.
Your other ranged options are kannon batteries (aforementioned), tankbustas (have to get much closer, can't just hang out in cover, have a rule that makes them retarded, don't kill AV 12 or less as well), rokkits in boyz mobs (bad idea, you want your shootas shooting at infantry and your sluggas running), or deffkoptas (vulnerable to assault, have to get comparatively close and thus take time and get closer to standard weaponry that kills them well.)
Last edited by Culler; 02-14-10 at 09:04 PM.