Heavycessors in Vanguard Spearhead

Has anybody tried running Heavy Intercessors in their Spearhead? Sit on an objective and have cover, -1 to hit, +1 AP Against D1 weapons, and still have access to armor of contempt. They seem like they would be pretty hard to shift, and can put out a lot of firepower at 2+ BS S5 AP-2 with strike from the shadows.