WotLK T9 set bonuses: How good are they?

[TotemsAreGreat]

I'm saving up EoTs for Unholy Spec while using my tank spec to spam RDF HCs and I want to know how useful the T9 set bonuses are for Unholy spec. Is it worth getting?

[angrylol]

It's definitely worth getting, better than 4 parts t9 is probably 4 parts 264 with perfect stats. Tough maybe that's changed since t9 2 part bonus procs less these days compared to times when I did some "tests"

[Xyriphe]

For my 5.9k uh (so way past considering the value of T9) with Bryntroll (the value of T10 2p increases with a slower 2h) in DK sim, stationary 5 minute boss fight:

Baseline with 4p T10: 11253 DPS (on a fight like Saurfang 25 my in-game DPS is more like 10.1-10.3k atm)
If I remove (only) my 2p+4p T10 bonuses: 10853 DPS
T9 2p only: 10974 DPS = 1.1% increase (this run in the sim reported 29.2% uptime, or 0.85 ppm if you don't take ICD into account)
T9 4p only: 11118 DPS = 2.4% increase (Blood Plague goes from 5.1% to 6.7% of overall damage)
T9 2p+4p: 11242 DPS = 3.6% increase (same number of 2p procs, same Blood Plague percentage)

Especially ilvl 264 head/chest/legs are going to be big upgrades over T9 ilvl 232, no matter the set bonuses. 4p T9 ilvl 245 might start to get a little muddier depending on whether you need the hit from off-set ilvl 264 head/shoulder/chest, but I was getting ilvl 264 drops before I had time to collect 4p T9, nevermind upgrading them to 245, so that never ended up a concern.

Considering joining ToC raids seems to often require about the same GS as low aim ICC, I'd prioritize getting the ilvl 245 EoT pieces like head/trinket/ring and buying ilvl 264 BoEs and choose 2p of T9 to upgrade to ilvl 245 along the way.