Viable.
Can't really recommend melee pets, though. They can do more damage in some situations, but bring a lot of problems, not least of them the "visual spam". Especially in T3, a Necro should be able to max out his damage (in regard to tank aggro) without the extra damage from going melee.
But that, of course, as always depends on equipment, tanks, skill, raid setup, personal preference, ... No feat setup can fix a tank having a disconnect.