Just looking for some clarification as this came up on a game vs another seraphon player. My understanding is that as wounds are delt one at a time, and assuming the guard fail any dpr saves, you can only allocate a maximum of 10 damage worth of wounds to the guard as they would all be dead and any excess wounds would go on to kroak/slaan. For example, I take 15 wounds, I roll 10 dice for the 2+ and then roll more dice for any 1s I roll for selfless protector. If I roll the 10 dice and 10 wounds are taken by the guard, the remaining 5 wounds are applied to kroak. However my opponent at the time stated that I roll all dice to go into the guard and any overkill on the guard is simply lost. Using the above example, I would roll all 15 dice for selfless protector and assuming they were all 2+ and the guard didn't make any dpr, the guard would take 10 wounds, losing the unit and the 5 remaining would just be absorbed by the dead unit. The second way didn't make sense because of the way quick rolling works, but he was adamant that's how it works, so just looking for another opinion.
Your interpretation is correct. Each point of damage is applied one at a time. So yes, you can only apply 10 points of damage to a unit of 5 Saurus Warriors, but you also apply them all separately. You don't have to declare all the attempts at once.
Selfless Protectors: Roll a dice before you allocate a wound or mortal wound to a friendly SLANN while it is within 3" of any friendly units with this ability. On a 2+, you must allocate that wound or mortal wound to a friendly unit with this ability that is within 3" of that SLANN, instead of to that SLANN. On the core rules about allocating wounds: [...] Some abilities allow you to make a roll to negate a wound or mortal wound allocated to a model; in this case the roll is made for each individual wound or mortal wound as it is allocated to the model in question. If the wound or mortal wound is negated it has no effect on the model. You have to roll one by one each wound, so when you've triggered 10 times the Selfless Protectors ability (or as many as your unit can absorb), you don't need to roll any more dice since they go directly to your Slann. Or better said, you've lost the ability that protects you from negating wounds.