In doing some Cooldown testing lately, I’ve been experiencing much the same thing, and have very similar Cooldown Reduction stats/gear to your own.
Mathematically, and using a very basic Cooldown formula, I would expect a 34% Cooldown Reduction to return something like the following times:
28/(1+0.34) = 20.89 seconds total cooldown
24/(1+0.34) = 17.91 seconds total cooldown
Using these rough figures, if you trigger the Digi-Clone first (for example), and with no duration buffs active, it lasts 15 seconds, then should be on cooldown for nearly 21. Triggering Barrier as soon as the clone disappears, means it will be active for 14 seconds, leaving 7 seconds of downtime waiting for the Digi-Clone Cooldown to be ready again. Similarly, triggering Barrier first lasts 14 seconds, then it cools down for almost 18, leaving 3 seconds downtime after the 15 second duration of Digi-Clone.
I’m finding that in non-combat situations, particularly in Sanctuary, and with the same gear/skills, there is no downtime at all, and the Action Skills can be triggered pretty much consecutively.
There could be all sorts of reasons for this. Perhaps the Cooldown mechanics are bugged in non-combat situations; or specific cooldown applications from GR, skills, or gear might be off somewhere.
Definitely seems to be a bug however, even if it doesn’t affect your combat performance adversely. From what you’ve said, the values you’re getting in combat seem about right, while those in non-combat are the wonky ones.
There are other posts on these forums noting similar issues with other characters too, so it’s not just Zane in this scenario I think.
Edit: The final figures were correct in my math, but a typo meant I’d used the wrong sign in one instance. Fixed now.