Iirc, it's 21 strength (and multiple attacks) in jaguar form (or was in D3, if my memory's not failing me. I really should go and check for D4...), which is pretty brutal for something as that's as cheap as those guys and rolling recruit-everywhere. They're a size larger in that form (which is somewhat of a disadvantage, in general), but still. Throw on quickness (The W9 bless) and something more explicitly damaging and you've got a furry shredder on crack. Gold for gold, the jags really are one of the best sacreds in the game just in raw stats, and the recruit-anywhere letting you mass ridiculous amounts of them is just icing.
And then the blood economy starts rolling in and oh gods, the everything.
As for afflictions, iirc form shifting like they do actually does have some sort of beneficial effect to it, if my memory's not failing me (though for the life of me I can't remember what, and could be mixing things up with some other piece of errata.). Plus... doesn't the jag form have regen? Which helps keep 'em from racking up, anyway. Could be mixing it up with the skinshifters (Which are very similar! Just non-sacred.) with the regen, though..
E: Woah, critical memory fail. They're base 13 str in jag form. Still have multiple attacks (good ol' bite/claw/claw). Base 18 HP, 5 prot. Fast, hit hard. Good defense, insofar as chaff clearing goes.