Your list is a one-trick-pony, as most everyone else has said, but, hey, it sounds like a fun army to put on the table, so if you really want to field this list, go right ahead.
That being said, you've been given lots of advice about what types of lists can destroy yours. Now, you should be asking the question of tactics -- how should I play this list to best effect against the various armies I'm likely to face at a tournament?
To answer that, it would help if you can describe the general types of lists you expect to face, if you know your local opponents well enough to give us that information. Otherwise, those who have offered examples of lists that will beat yours could follow up with suggestions for facing them successfully.
I, sometimes, play a highly mechanized list with a Combat Squaded Scout Squad, so can tell you how I use them. First, the Scout Squad should have five Snipers which, when Combat Squaded, can be infiltrated on an objective, or in the case of Victory Points, in an elevated position with a good field of fire. The other five should be equipped with Bolt Pistol/close combat weapon witht he sergeant having a Power Weapon or 'fist and, maybe, a Combi-Flamer or -Melta. This Squad can be held in Reserves if you think there will be a good target of opportunity or, more commonly, placed in a position to protect the Snipers from assault. The entire unit should be equipped with Camo Cloaks.
Realize that the main purpose of these two Combat Squads is not to deal damage to your opponent, but to draw his fire away from your other units. Going to Ground in Cover (4+) with Camo Cloaks gives these squads a 2++ Save. As small as they are, they can survive for a very long time under heavy fire. Don't worry if they remain pinned (Gone to Ground) every Turn. That just means that every Turn your opponent is wasting fire from one or more of his own units on them.
The rest of your army list is short-range fire. So, embark the Terminators in one of the 'Raiders and advance into your opponent's face. Since you only have one Terminator Squad, that 'Raider should shoot forward as far as possible first Turn, but the other two don't have to move more than 6". Your Captain should be joined to the Terminators. If you have the points, you should go ahead and give him Artificer Armor, but don't bother with giving him Terminator Armor. He already has a better Invulnerable Save and you'd be spending more points for the 2+ Armor Save and losing other options (like Sweeping Advance if he leaves the Terminators and joins another unit or goes off on his own).
I hope this helps,
NewHeretic
