Sure, but the things is not to lock yourself away from the aggro.
If a DT tank is getting seriously hit, and you, as a guard, try to take the aggro back: With Call to Arm, you might give more aggro to the DT (since his aggro is DPS based) than what the pure hate buff CtA gives you. The situation is now worse, since the DT which had the aggro is now about to die and you still don't have aggro
So yeah, Call To Arm can be useful but I think Buyten was just saying you should be careful whit it.