What's wrong with 2 Rangers with 20% giving a total of 40%? If Warding is capped at 70 it's fine if they stack. I can't imagine many players are going to take 2 Rangers anyway since you are realistically limited to 5 heroes so 2 being specialized Warding units doesn't give you much else hero wise.
Piranha I'm happy you changed Ambush back to instant kill. Now it has value again as a deterrent against strong stacks.
2 points of path finding for the Ranger to start with seems right. Most times I expect players won't buy him till mid game when dealing with Assassins since he isn't needed in the early game. So at L2 or L3 you can immediately purchase a 3rd point to get his movement down to 3 in hills/swamp or even a 4th point to get to 2 movement.
As far a icons go, you definitely need to find a group icon for all the group related skills you now have. It could be that the group indicator is different shape (circle/triangle/octagon instead of the square) and/or background color around the symbol in the middle. Or maybe instead of the outline of the square being a line it could be a bunch of small men. If you look here you can see some examples of group icons http://findicons.com/search/group that you might be able to add on to the existing icons to indicate stack related.
KGB