If the leader was a popular one it might be as likly to encourage as discourage, "fallen captain to avenge".
Also though the K'kree think more collectively than humans, that doesn't make them a mob. They are trained soldiers and if they are hindered by racial instincts it is unlikly to hinder them so much as to make them lose all discipline the first time something goes wrong. You can't assume they will act like "peasants with pitchforks".
Actually what they probably do his have a series of stereotyped manuvers that they learn by rote. Of course all armies would have that to some degree, but the K'kree would do this more.
K'kree are actually hard to calculate because they are far more different from humans than are Aslan, or Vargr. For one thing sense they are not carniverous they don't as firmly based of an instinctive talent for tactics, everything had to be artificially developed. This is somewhat true of humans too but hunter/warrior instinct goes back farther. As for Aslan or Vargr...
K'kree are not natural warriors the way humans, or Aslan or Vargr are. Of course that begs the question of what we mean by "natural" but as far as the subject at hand you see the point.
K'kree can be counted on to be brave and disciplined. They probably have a high degree of cohesion though that is weakened when the "anti-grief" drug starts to wear off-K'kree can't put their emotion on hold as easy because of the Herd mentality. Also an individual K'kree can carry a considerable ammount more firepower and armor.
However K'kree would have a low degree of initiative. Despite their "horsy" appearance, they are really more like infantry than cavalry.
What they might do is use specialists from vassal states to herd(no pun intended) enemies into a killing zone where the K'kree would grind them down. K'kree would also use a lot of artillery. When the final rush comes they would have a considerable ammount of elan that would carry them on. When that comes it would be VERY hard to stop.
Their chief disadvantage woul be in space where everything depends on manuver and stealth rather than shock. But perhaps not. They can use something simmilar to the ground tactics-have specialists, likly aliens find the enemy fleet, than rush down upon it and force a slugging match("no K'kree can do very wrong if he puts his ship alongside that of an enemy). Of course K'kree ships can't carry as much firepower to the dton, as others can, but they definitely can't play hide and seek.
Perhaps the K'kree's biggest advantage is their unity. Human,Aslan, and Vargr are always disunited. So the K'kree can always choose a war where they will have overwhelming advantage. If they ever meet the Imperium they will be in trouble. But that hasn't happened yet.