Terminator Armor already grants you +1 attack which I've always taken to mean that you cannot get another +1 attack for being armed with two close combat weapons (as per the rules on p40 of the BGB under "Attacks"). I don't know anyone who plays GK Terminators getting 3 attacks each round. They follow the standard "shoot assault weaponry (or heavy since they're Terminators), charge with +1A, then use profile # of attacks for next round" routine.
Moving slightly more on-topic: If I were to change your list in any way, I'd say keep the GM with retinue, Crusader and the two dreadnoughts. Increase the size of your two mandatory squads to make them more durable and keep the psycannons there, then merge the two fast attack choices into one squad, using Incinerators instead of psycannons. However, the list is perfectly playable as it is, and the changes are more due to my own personal playing style than anything else. I'll explain why just in case you might want to know ;-)
First off, I always felt the Incinerator to be a perfect Deep Strike weapon, but if you're kitting them out for light anti-tank, stay with the Psycannon. Personally I equip my fast attack squad with one or two incinerators, a complement of 10 men, and kick them next to some juicy heavy weapon squads where their massed Storm Bolter and Incinerator fire can really do some serious damage. In my experience this has been highly effective, whereas by targeting tanks you will waste a lot of those precious Storm Bolter shots. I say let the Dreadnoughts and Crusader deal with the armor, that's what they're there for. Keeping two squads in reserve and waiting for them to deep strike can also wreak havoc with your game plan, whereas one squad will usually be able to do some good SOMEWHERE on the playing field.
That being said, I also prefer the Grand Master over the Brother-Captain. That force weapon is just too good to give up. I still remember the time he took out two Hive Tyrants single handedly and then charged a bunch of termagants... *sighs* Aaaah, those where the days.
On the other hand, he DOES cost a lot of points, you DO lose the ability to use Holocaust every assault round (as the force weapon is the only psychic power you're allowed if you use it) and a Brother-Captain will usually be more than enough to lead the rest of your Terminators to victory. But, if you regularly face off against armies containing nasty beasties (Hive Tyrants and Wraithlords spring to mind), I'd stay with the Grand-Master
Personally I always maximize my Terminator squad when fielding a Land Raider Crusader as 8 Terminators jumping out of that thing is nothing if not impressive. Furthermore, the Holocaust rules states that the ordnance template be placed "anywhere in contact with the psyker" meaning that with some clever positioning you can avoid taking any hits on your own squad whatsoever. I don't really see how anyone could call Holocaust dismal. For 20 points you get to inflict a S5 hit on pretty much everything left standing after the Terminators are done swinging their force halberds, and if you're going against lightly armored swarms this is invaluable. Besides, the risk of suffering a PotW hit isn't all that high, and I'd definitely say it's worth it.
There's no doubt that an all-out Grey Knights army is a tough army to play. However, the sweet feeling of accomplishment you get when you actually manage to smear the battlescarred wasteland full of the filthy corrupted remains of the enemy can only be described in one word: Priceless!
Enjoy the tournament in Florida, acekng1. And remember: The Emperor Protects!
