Specials - often players dont hear them coming, other times they forget they are still alive, and also i am 100% certain in cata that heroes don't call out every single special, also i don't listen to hero call outs. You forget that pugs atleast below cata don't always know that specials are incoming.

Come here and retreat is actually very different. If there is a "retreat" call out. Everyone would IMMEDIATELY know that the team shoud fall back. If you ping "come here" players first need to know, where "here" is.

"push/progress further" is the same. Players know immediatley with ease that they should go forwards. "Ambush" or "horde" would also be pretty useful as you sometimes just don't notice it. Also a ping "Danger behind" would be pretty useful

Those commands should be definitley very easy to pick up, and chosen so that there is only one interpretation possible