All factions get double frags except Chaos. Orks get double Stikbombs, Eldar get double Plasma grenades.
Running around with my Vulcan Melta I can kill any Eldar tank in 1 overheat without Krak grenades or Melta Bombs. I can take out Trukks & Rhinos by firing and then stopping just before overheating and then firing again once it is 50% cold. Predators and Gun Wagons take 2 overheats. Each faction has its ability to just shut down vehicles. The issue is getting people to play them, The Eldar are much more specialized so it comes naturally.