That's what they always were. None of their games is completely original - it's practically their signature to take good ideas from other games on the market and mash them together into a polished(YMMV) product of their own. Starcraft took a lot from the Dune games IIRC, Warcraft 3 was a remix of SC mechanics with a bunch of new ideas thrown in, Overwatch takes a metric TON of ideas from Tribes, Global Agenda and Team Fortress 2. The only games I can't think of anything for are Diablo and Diablo 2(And the Lost Vikings of course).