I think the auto-defend that units perform instead of other actions has gone a long way towards mitigating first strike advantage.  

However, my Impulsive high initiative Sovereign on horseback has little problem reaching the opposing enemy before those units even get to auto defend.  When placed on a small tactical map he reaches them and gets 2 actions before they get to move.  Needless to say his Druss blade + sweep + high level makes short work of opposing groups of units.  

Maybe that should be an advantage to having a Sovereign with that particular setup & gear, but having units start the battle defending would mitigate the problem too.  It may cause other problems, I'm not sure, but it would stop you from decimating what should otherwise be a relatively hard hitting force before they even get to move.