I'm no mathologist, but I'm pretty sure that with regards to the seafoam green parts of this chart:



It clearly states that comboed abilities generate much more hate per second. I don't have a degree in the arcane arts of mathologica, but I'm pretty sure that 750 times 3 is less than 3075, meaning maybe you should spend less time misreading charts and more time actually tanking where you would quickly find out that comboing your threat abilities makes it so you can actually hold threat, something you said you had a problem with.