In my opinion, your only real downside with your warband is movement. Vanguards only travel 4 inches as standard so unless you get lucky with some doubles or trebles, it'll take you a couple of turns to get into melee range or reach of objectives. And I'd be careful with relying purely on the bows for damage. With some of the twist cards, the range for missile weapons is reduced rapidly over the turns or done away with completely so you don't want to be left without some means of attack.
I've got 2 SCE warbands prepared, one with 3 Hunters (one is the prime) and 3 gryphhounds (the hounds for pace, melee and objective grabbing) and another with 1 Raptor Prime with Hurricane, 3 Hunters, a gryphhound and 2 Aetherwings (again for objective grabbing). Both give me a reasonable (not great) mix of movement and attack. Eventually I'll drop something to get an ally to bolster my melee.