See Valos, Land of Conquest.

Second ability is pointless, as once he's dealt damage the other creatures will have also, they won't get the bonus until after combat. Also incredibly overpowered for 4 CMC.

I'm not very good at gauging power level, so I'll have to trust you there. However, you're wrong about the triggered. He has first strike, so he will boost all of your creatures without first strike before their combat damage is dealt.

Forgot about the first strike, I just skimmed over it. Power usually costs more than toughness (see how Steel Wall has 4 toughness for 1, but Elvish Ranger has 4 power for 3? Now add in haste, which is the R, and first strike + the other ability which is probably W or 1W...) I'd say that the CMC should be either 2RRWW, or you remove the haste and make it still RRWW. That second ability is a really good finisher, and haste makes it almost impossible to predict, especially if the opponents has recently attacked with all their creatures.

Mythic, manofperson, Mythic. 2RRWW is the exact casting cost of Aurelia, the Warleader, which is clearly a stronger card than this card, and isn't even a tournament staple.

Right now, this card is a little better than Hero of Oxid Ridge, with one more toughness, first strike and one bonus power to your creatures (though the Hero also featured blocking restrictions, and a bonus that applied even when the opponent chump blocked). The bonus to your creatures balances, and yeah, I think the double white covers +1 toughness and first strike. But it wouldn't be out of place to make this cost 1RRWW.