I can definitely see the downside to ever going derensive using a 2h, half of the abilities in def require a shield, and yeah you might gen a bit more threat, but you have to weigh the lost threat from lowered dps, lack of damaging abilities. As a 2h tank you’ll get most of your threat from just keeping up with dps and sprinkling in some higher threat abilities.
Using 2h would also boost cleave by a wide margin as you aren’t cleaving with a fast 1h that will spred 20dmg to all targets, you’re smacking a bunch of mobs for a high threat 200-250 damage easy. And if you’ve balanced agi into your gear there’s a good chance for crit which makes cleave practically a sunder by itself, two on crit.
Although at higher levels this will probably cause some MASSIVE healer stress.