Shadow Priest: Bug or working as intended?

[Riplin]

Playing my first priest I hit 60 not too long ago and basically lived in AV this weekend. First of all I love the shadow priest for pvp. This is my first character where rogues really aren't an issue, unless they outgear me by quite a bit. I don't raid, ever, so this weekend in AV is the first time I noticed a real problem with the shadow priest.

When fighting something with an entire raid I found myself almost entirely ineffective. Most of the time I just switched to healing. I am wondering if the problem is related to the 8 debuff limit. Here's what's happening:

Immediately after landing SW:P or Devouring Plague they disappear off the boss. They land (not resisted) but immediately disappear.

Mind Flay is similar. It doesn't get resisted (I have the 10% resist talent also). It simply stops before it even ticks once. Of course it still uses the full mana. I'm thinking it's because it has the snare component which is considered a debuff, and is therefore subject to the 8 debuff limit.

Consequently, I'm limited to only casting Mind Blast with it's long cooldown. I can't SW:P. I can't Devouring Plague. I can't Mind Flay. This completely neuters the class in this role.

Interestingly enough, both Vampiric Embrace and Shadow Vulnerability (Shadow Weaving) stay on the target with no issues.

So, what is going on here? This surely can't be intended.

[Ana]

Debuffs are prioritized, stuff like curses or shadow weaving have high prio so basically nothing ever knocks them off, mindflay or SWP have... not so high prio.
You're basically encountering the exact same problem shadow priest has in PvE. There's a reason why basically no raid takes a shadow priest before 16 debuff slots.
Stick to attacking enemy players and you should be good

[Riplin]

So I'm reading the limit was originally increased to 16 in patch 1.7 so I assume we'll get it on Nostalrius at that point. This is still a small number and really gimps classes that rely on dots for a greater portion of their damage.

In TBC it was increased to 40 and removed completely in later expansions.

[Prancinglid]

When ZG comes out in the next month it should include the increased debuff limit.

Yea, it does suck, but it isn't really "broken". Aside from not being able to do damage with the debuff slots, spriests don't have a lot of the gear available until ZG to actually compete for damage since there isn't proper hit gear for PvE (except for neltharions which will be BiS through Naxx, but GL getting that on a priest anytime soon!)

ZG brings us bloodvine and cloak of consumption (among other things) along with the increased debuff slots, and I think this was done by design. Plus, warlocks from here on out will just gradually become the stronger dps class so maybe having some time in the game where they aren't getting an additional 15% bonus is blizzards way of balancing it out... Lol.

[Ana]

To me that's just broken design

Vanilla is broken in general. Welcome

@up
Actually shadow priest is THE dps class that doesn't really need too much +hit to function properly. Although it sort of balances out, because their ZG enchant is completely useless...