Who said anything about bullrush?
(bonus points, use a minion to grab the Cleric: Immobilize... at-will, yeah, that is super rare, and against a Wis/Cha Cleric's weakest NAD).
I brought up bullrush because it is the one method that all characters have to move enemies around - it's just that it's usually too weak to be considered an acceptable solution. This follows a similar line of reasoning to your mention of grabbing with minions... and suffers from similar problems: outside of dedicated grabbing powers, a grab tends to be a poor use of a standard action.
By the way, I think you greatly overvalue the strategy of grabbing with minions. Though not insignificant, a grab is quite weaker than an immobilization, since the character has a chance to make a check to shift away. Not only that, but killing the minion (which usually takes little more than staring at it) will automatically end the grab. Having standard monsters do the grab would be far more reliable, though also more costly.
People only think Consecrated Ground is "overpowered" (ugh) because they don't understand how fragile it is.
(...) Now it is completely trivial for the DM to focus the Cleric and move him out of the zone with standard monsters.
I'm afraid I must disagree about its fragility. I just don't see that many 4+ forced movement in monsters (as anything less is usually pointless since the zone can easily be moved 3 squares), and even then you're not guaranteed to kill the power, as the cleric will often be able to double move the zone, or provoke an opportunity attack, or shift+charge, or be moved back by an ally. This means the zone can be disrupted for a turn or two, but it won't easily end. Stuns and dominations are a much more real threat, as with most 'sustain minor' dailies, though feats like Superior Will provide reasonable protection against that.
Admittedly, I wasn't aware about the range rules for maintaining Consecrated Ground and powers like it, before this thread... and this is a point that has forced me to reevaluate these powers. It's just that I don't see it as such a big deal - just an inconvenience.