Colossus will do significantly more damage for about the same amount of Defensive power as Thane.
While thane will somehow make you think you’re taking less damage due to you spamming ignore pain more often it doesn’t exactly correlate to being better defensively since Colossus has a 20% stronger ignore pains per cast, it’ll also build more ignore pain shielding through it’s higher damage via Brutal Vitality, that’s not to mention Colossus takes 5% less damage as well at all times due to Mountain of Muscles and Scars, higher mitigation via crit blocks through Martial Expert.
By all means if you enjoy the Thane playstyle nothing will be stopping you from timing your 10s, however learning how to play Colossus correctly will net you both better throughput and a better defensive profile for larger pulls due to the passives Colossus has access to that Thane does not.
That and Demolish crits still make you giggle like a schoolgirl every time they pop off 