we have an improved berserker stance, and an improved defensive stance...so why not an improved battle stance?
make it deep, just like the other imp stances, possibly replacing imp MS with it (since imp MS is crap rolled in **** tossed in *****). make it a 5-pt talent, and have it increase your chance to avoid (resist, miss) all attacks made against you while in battle stance by 1% per point and increase the critical strike damage bonus of all attacks made while in battle stance by 3% per point.
it gives incentive to use battle stance as more than a stop on the way to Overpower Blvd. or Tclap Way. with impale youre looking at 35% increased crit damage, which helps a lot in both pvp and pve affecting specials and 15% more crit damage on white hits while also providing a nice extra defensive boost. it synergizes well with other talents in the arms tree, even with ER to an extent (with the white damage crit bonus boost helping to feed more rage), as well as impale and 2h mastery.
of course, this is just *my* idea. others are, of course, welcome. ideally id think it would be something that could be useful in both pvp AND pve, but not overpowered in either. obviously imp battle stance is limited to affecting battle stance, so you wont be tanking with it (10% global reduction in damage is better than a 5% higher chance to be missed or resisted), but it provides an extra bit of protection while dpsing in a pve environment as well as giving arms warriors some extra damage and mitigation in pvp (in other words, battle, the balanced stance, receives bonuses that help a little in both offense and defense).
i suppose this is my long-winded way of saying "make deep arms worth it". i like flurry and sweeping strikes and imp execute and all, but id like even more to have a reason to spec past 35 points in the arms tree.