In reality the powers weilded by Ashton will be relatively modest and most of her actions will scarcely be noticed. It seems pretty clear that she is Brown's fourth choice and even further down the list of the other 26 dinner party guests who would have known little or nothing about her. They feel they can control the frst High Representative. However the Lisbon Treaty is so constructed that powers can be progressively transferred to the role through ratchet clauses. Ashton may not have all that much power but her successors may well have real power within the same role.
Right now we have an unelected senior post with ill-defined powers and ill defined accountability within a system which has been created with a view to increasing those powers over time without increasing the accountability. Even the government of the USSR didn't come up with anything this fiendish.
As with everything the EU does it displays infinite patience. They have realised that there would be problems right now with high profile appointments so they have made them low profile. This will change in a few years' time.
