I do agree that most warlock builds in 5e are underdogs (mostly because most groups do 1 or 2 encounters per adventure day), but it must be said that there are some amazing Hexblade builds you can make. Though many would consider those builds munchkin builds.
The solution should be to limit long rests. It is when you have many short rests, and few long rests, martials, warlocks etc get to shine.
