Where's your rogue!? Sap lasts two minutes and twenty seconds when glyphed, it never breaks early by random chance, you can set it up before the tank pulls without fear of starting off the fight with everything glaring at you, and to top it all off you can pickpocket your sap target just to rub it in his face that he's about to get roflstomped AND lose his lunch money. As a rogue, I will fearlessly charge into unknown groups to test sap on every single new mob I meet to bring more convenience to the tank, I have no issues with sacrificing my dps to spend my time chain stunning a caster mob if that's what it'll take to get the pull done, and all dps should learn to play this way.
As a tank (warrior) I declare my cc markings at the start of each instance (sap star, sheep moon, banish diamond, root triangle, mc circle, etc) and will mark them as I feel they are necessary. If my CC fail to get their cast off before I MUST TC or Cleave to establish threat then I will consider the attempt on crowd control a failure and will tank the mobs without it, bite the bullet and start running the cooldowns. With enough runs, tanks will be wearing enough dungeon blues / rep and crafted epics to handle most pulls without the use of cc.
When you run random dungeons with pugs my suggestions:
1: If you want CC used, say so at the beginning of the run and be clear about how you want it executed (do you want a sheep pull, a trap pull, or do you want cc cast After your opening attack), be clear about which marks you will use and stick to them.
2: If a form of CC is failing, try to approach the problem from a different angle, sick a rogue on a caster to chain stun it so it wont start harassing the healer, or get a hunter to kite a "Myrmidon" or "Axemaster", utilize roots and mage snares to tangle up melee mobs and be sure to tell your group to stay the hell out of whirlwinds!
3: In the end of things, the tank is the final and most absolute crowd control. A well timed shield wall/divine protection/icebound fort can and usually does make the difference of survival and death in the face of a horrible pull. Don't panic, all of the tools are already available it's just a matter of using them to secure victory.