Instead of having a tiny buff, or no notification of how long, why not have the time remaining until a skill cycles back counting down over the skill? Instead of being the time until cooldown, it would simply let you know how long you have until you can’t use the cycled skill.
Basically, skills like infiltrator’s strike will cycle to another skill (in this case shadow return) and back after an amount of time, giving a constant countdown over shadow return’s icon. I use infiltrator’s as an example because it’s probably the most prominent skill that would benefit from my idea, but it would be useful to know when others are going to time out as well, like the ranger sword leap.