The concept of a dog attack should be simple enough - when you let it get close and you die, you deserve it. If you complain that you were unaware or you were not paying attention leaving a dog inside your building then that's your problem. Now why would you need a squad to kill a dog, you should be able to kill it by yourself with basic infantry.
Hence - a dog should have low health and no armor, it should resist few bullets or pistol shots max, everything else hitting it should kill it. Any soldier has range advantage.
And perhaps you can also try this - instead of never-ending insta-melee attacks, give the dog an attack that requires a cool down, which would:
1. Limit the dog to attack one infantry at a time with targeting mechanic
2. Give it a visual and restricting vulnerability before he recovers from attack - if possible, make the attack animation last for few seconds with recovering animation as well -> then it's easy to take it out (imho this was also how it was in RA, the dog couldn't always attack right away and was vulnerable biting the enemy infantry on ground)