The fact that troops gain pooled XP has been around since the predecessor games and I believe it works well. It is an effective compromise between every individual troop having to make its own kills to level up which would be tedious vs the entire army sharing its XP evenly which would be dull and lifeless. A player doesn't need to understand exactly how it is working to play well, but a player who does understand the details can make a few little optimisations to gain tiny advantages - that is the mark of a well designed gameplay system.
The only time I can think of where this doesn't hold true is the Train 10 Troops quest. If you don't understand pooled XP and upgrade troops as you go, you make life much harder for yourself than waiting until enough XP has been earned to upgrade the lot. I'd say the issue there requires changes to the quest rather than changes to the XP system.
Though the design of pooled combat XP is fine, currently there are other aspects of troop pooled effects which are just plain busted:
* Healing. 5 recruits of 1 culture take 5 times as long to heal as 5 recruits each of a different culture because the healing rate is applied to each stack.
* Prisoner recruitment. The chance to recruit from your prisoners is calculated per stack also. As such you can recruit 1 recruit from a group of 5 per day (I think the default chance for a level 1 troop is 50%). But you get a 50% chance for every troop if they are recruits of 5 different cultures and thus each in their own stack.
* Raise the Meek/Combat Tips perks in the Leadership skill. They apply an XP bonus to a stack. Same deal as the others, this means it is optimal to have many small stacks because a large stack only gets the same amount of XP per day as a stack of one.
Basically, all concepts of this type should apply to individual soldiers and not stacks. The XP perks, prison recruitment algorithm and healing rate calculation are all effectively broken. Pooled XP from combat is fine.
The only time I can think of where this doesn't hold true is the Train 10 Troops quest. If you don't understand pooled XP and upgrade troops as you go, you make life much harder for yourself than waiting until enough XP has been earned to upgrade the lot. I'd say the issue there requires changes to the quest rather than changes to the XP system.
Though the design of pooled combat XP is fine, currently there are other aspects of troop pooled effects which are just plain busted:
* Healing. 5 recruits of 1 culture take 5 times as long to heal as 5 recruits each of a different culture because the healing rate is applied to each stack.
* Prisoner recruitment. The chance to recruit from your prisoners is calculated per stack also. As such you can recruit 1 recruit from a group of 5 per day (I think the default chance for a level 1 troop is 50%). But you get a 50% chance for every troop if they are recruits of 5 different cultures and thus each in their own stack.
* Raise the Meek/Combat Tips perks in the Leadership skill. They apply an XP bonus to a stack. Same deal as the others, this means it is optimal to have many small stacks because a large stack only gets the same amount of XP per day as a stack of one.
Basically, all concepts of this type should apply to individual soldiers and not stacks. The XP perks, prison recruitment algorithm and healing rate calculation are all effectively broken. Pooled XP from combat is fine.
