A lot of the perks that are currently in the game are OP in part because its so easy to gain/regain WPs.
I thought originally that the idea of will power was that the player would have a decision to make in whether or not to spend those WPs on perks in order to boost abilities and what not, but that this would come at the cost of lowering their Will for the remainder of that mission. That would have presented the player with a genuinely interesting dilemma.
However as it stands, being able to gain additional WPs so easily via rally the troops, killing enemies, and special map tiles means that spending WPs is a no-brainer, especially in the situations where you know that you’ll get those WPs straight back.
What I’d propose firstly is that whenever WPs are spent that both the current, and also maximum WPs of a soldier are lowered. So you start of with 8WPs, spend 2WPs to use an ability and now have 6WPs, but the maximum that you can top back up to is now 7WPs.
For Rally the Troops, I think you absolutely need to make the cost of using this skills be higher than the WPs that can be given via it. If it costs X amount of WPs to use, then that should be per solider that you’re boosting, and that amount of WP boost should be a percentage of the WP boost given.
For killing enemies, I don’t think this should give any boost to WP at all, unless maybe that solider has a passive skill that allows for it. Likewise, I don’t think it should lead to panic in enemies that have high WP to begin with, and/or aren’t within an immediate range of that enemy being killed.
For WP boosts on the map, I actually think this is quite good, as it gives a strategic objective for the player to move towards… maps should be larger/longer and dash should be nerfed in order to make these points harder to reach, the distance between them needs to be further than a single solider can move in a single turn.
Beyond that, I think you could also give solider’s an additional WP penalty at the start of maps that is based on their current level of stamina. Again a passive perk could exist to negate this.