I've heard from the healers that I'm getting hit really hard and they can't keep up with the damage..
Is it me that needs better stuff, or are the healers (s)lacking a bit?
EDIT: I'm not sure if it's a fair comment or not, but apparently I'm ".... a crap tank because I keep dieing...". This was in the Onny10 raid. It's not like I loose agro or anything, quite the opposite..
I'm not experienced at all, but if you are MTing boss mobs, you could probably replace all 3 of your major glyphs. Cleaving can be replaced as you aren't AOE tanking, and HS/Revenge can be replaced because on a fight such as the ones you mentioned you should never be rage-starved.
I would suggest removing the 2 points you have in Improved Cleave, put them in Improved Disciplines, then replace one of your major glyphs with Glyph of Shield Wall. With those upgrades, you will be able to negate a lot more damage with a Shield Wall every 2 minutes.