each instance of cooldown reduction is a separate calculation. so first one is 26% of 60secs to reduce it to 44.4secs. then the next 20% is of the 44.4 to further reduce it to 35.52. etc
btw there is also a cap they introduced to cdr. i dont know it off the top of my head
Combine your CDR with strategic ground stomp which reduces your ultimate by 2 seconds for each enemy hit. Ground stomp size increase will hit more enemies and you can have WoTB up easily close to 100%
You always have to trade off something to get what you want out of a build. I used to do this with walking aresenal for constant back to back iron maelstrom in prior seasons before we had the size increase. I even did the unthinkable and put on 100,000 steps for even more GS procs.
When it comes to calculating multiplicatively-applied reductions (damage reduction, cooldown reduction, etc.) it’s helpful to calculate it in terms of what remains, not what gets reduced. For example, a 20% reduction (80% remains) and 40% reduction (60% remains) would get you:
(.8 * .6) = .48 of the original value, so a 52% reduction.
(.891 * .906 * .797 * .799 * .84) = .432
That means your cooldowns are 43.2% of their normal values, which is a 56.8% reduction, which is probably within rounding errors of the 56.6% your stat sheet reads. Everything seems to be in working order.