The tooltip on the ability button remains the same regardless of which passives you have / have not selected, your CDR and any set bonuses / items that can reduce it. For example, in my WW/Rend build, the Obsidian Ring of the Zodiac causes the cooldown to be way less than 120 seconds (without Boon) or 90 seconds (with Boon). In IK/HOTA, you could test the cooldown just stood in town hitting the ground with your hammer and you could probably get WotB back up in under 10 seconds.