edit: mostly sniped
Status effects damage accumulates in a unit. The % shown on healthbars is in proportion to the unit's current health (for example if the unit has 600 current health and 25% slow and 40% disarm, that means it has accumulated 150 slow and 240 disarm damage). EMP and Disarm apply their disabling effect if they exceed the current health, i.e. are above 100%, and do nothing otherwise. Slow applies at its current %.
EMP and Disarm decay at 2.5 %/s (regardless of current health) so that is how damage translates to duration. For example if a unit has 110% EMP (eg. 2200 accumulated EMP damage vs 2000 health) then it translates to 4s of stun. Slow decays at 4 %/s.
How much damage a unit can accumulate is dependent on the attacking weapon type, usually expressed in time. For example Faraday can stun up to 2s which means that it can add EMP up to 105% of the unit's current health. All EMP units can stun for at least 1s.
Slow damage's effect is capped at 50% and all slowdamage units can reach this value. Some units can stack the damage higher but this does not amplify the effect, just keeps the unit at 50% longer.
If a unit's current health changes, accumulated EMP and Disarm get scaled to keep the % the same (but further damage is more potent relatively). Slow doesn't scale so doing damage to a slowed unit will amplify the slow.
EMP damage also applies Disarm damage, but as long as they are equal this isn't shown (so if you have 50% EMP and you get 10% disarm, you now have 50% EMP and 60% disarm).
Status effects apply to shields at 1/3 of their nominal value, plus whatever real damage they usually deal (for example Knight does 240 real + 600 EMP damage, so to shields it deals 440 damage (240 + 600/3).
