Lucian is good, but there are better combos.
Lets say it's 35% (that's a bit high, but just for the sake of math).
If Lucian has max rank Q, rank 1 W, and rank 2 E, his highest possible total basic ability CD's would be 43 seconds. This means that, over the duration of the tether, each of the 3 abilities would have their CD reduced by 1/3 of 35% of that number, which works out to about a 15 second reduction across the board or about 5 seconds per spell.
This means he'd halfway refresh his Q and get some good progress towards another W and E.
If you want something insane, look no further than Warwick and his 120 second CD W breaking this interaction.
For WW, the total CD would be 140 seconds if he's maxing Q>E>W.
That works out to Karma reducing his CD's by a combined 49 seconds or by 16.33 seconds per spell.
This means that Warwick would get to use his Q three times in two seconds.