Currently, the level 15 elite skll, Endless Pulse, reads:
Consumes an extra 40% of current HP and
increases Physical Attack Speed by 2.0% ... 7.0%. Also recovers 5.0% HP
every 2 seconds for 8.0 seconds.
The level 35 elite skill, Indomitable Spirit, reads:
Can only be used when HP is less than 65%. The following 3 Dark Energy Strikes cause double the damage. Also restores 2.0% HP.
Clearly these 2 skills were meant to be a combination, which is a good concept. However, their cooldowns do not match. Endless Pulse cooldown is a long 20s, while Indomitable Spirit has only a 7s cooldown and 30s duration. This makes using them together effectively quite difficult -- you have to endless pulse + indom spirit 10-20s before you intend on using Dark Energy Strike, so that you can once again buff yourself using the combination. While I will acknowledge the fact that you don't need Endless Pulse to drop your hp below 65% to use Indom Spirit (monsters hit you, you're tanking bosses, etc), it limits the effectiveness of what appears to be a damage-oriented champion combination (rather than a tanking oriented one), since you won't be taking direct damage.
The weaker of the 2 skills is clearly endless pulse --- The attack speed increase is quite small, meaning the main purpose of the skill is to allow the usage of Indomitable Spirit. But since the cooldown of Endless Pulse is 20s, where as Iindm. Spirit is only 7s cooldown, this doesn't match up well.
I would like to see one of 3 changes to the Skill Endless Pulse:
1) longer duration. This would make the skill more impactful outside of the Indomitable spirit set up. Let's say 16s duration, restore 2.5% hp every 2seconds
2) Lower cooldown. Keep everything the same, but shorten the cooldown to 7 or 10 seconds, so it can be combined with Indomitable spirit more easily
3) A better Effect. Increase the attack speed bonus from 7% maximum to 15%. This makes the short duration of the attack bonus much more impactful, while maintaining the current level of synergy with Indom. Spirit. By improving the effect, the necessity for a shorter cooldown is negated.