The real question is why the Dominion would even allow their troops to attack and possibly harm Odo, when
- the whole point of the whole thing was to bring back odo
- AND the dominion had perfect control over the situation?
Which attack are we talking about?
In "The Search", the Founders probably honestly didn't know Odo would be aboard the intruding ship, and didn't prepare their Jem'Hadar for the possibility.
In "The Die is Cast", it is possible that the runabout where Garak and Odo were fleeing was arranged some special protection, and that the Jem'Hadar just faked the attack against Odo. Then again, it's equally possible that this was a typical fog-of-war situation where Odo was on his own - there'd be no active effort to kill him, but no possibility of arranging for his protection in the battle, either. Ditto for the Klingon rampage in "Way of the Warrior" - the fake Martok wouldn't have been able to orchestrate every little detail of it, but he could have assumed Odo would survive no matter what.
In "The Adversary", the hostile Founder might have intended to save Odo whilst killing all his friends - but when Odo sided with those friends, the Founder might well have made the decision to kill Odo, as surely was the privilege of Gods. Besides, the Jem'Hadar would never find out about it anyway, so the Founder could do anything and everything without endangering the loyalty of the troops.
The "we don't kill each other" thing is obvious propaganda to begin with: clearly, individual Founders disagree with each other, and sometimes these disagreements come to a sharp point. But a feeling of unity against Solids no doubt does limit Founder-to-Founder violence to a minimum.
Timo Saloniemi