Taclord used lead the attack in my last game - which was actually very good for me, as he used it on a higher level elite soldier I had in there (he's to be a reoccuring NPC, so I want the players to start off weaker than him), and it brought his defences down from ungodly to a bit weak. Then he got pushed down a hole he couldn't climb out of - it worked very well story and gameplay wise.
That said, I can see it being potentially a problem - but I also like it because it makes throwing over leveled baddy NPCs at them viable.
I guess my biggest annoyance is the amount of healing the cleric can pump out, even post erratta. It makes it hard to make an encounter difficult but not grindy - by the time I'm getting through their healing triggers, they are also through their powers. It also makes for short aventuring days - to challenge them, I have to make them blow more surges in an individual encounter, which means fewer encounters per day. Doesn't help that we also have a warlord - but its better now that he's retrained his extra healing feat for a feat that boosts the attacks he gives out - I love that one, it turns all our other characters into strikers, at least for their attackes on the warlord's turn.
I think I'll have to try some encounters where I seperate the party more, and do more focus fire, which is something I generally avoid. So long as I don't focus fire the same guy all the time, it should work.