We use the Lipton French Onion Soup mix for pot roast too, but no other broth. Soup mix, water (3/4 covered like you said), and meat. Cook slow, at least 4 hours.
Do not add potatoes or carrots until it's mostly cooked, if you add them at all. Potatoes suck the salt out of the broth and make pot roast tasteless. I prefer garlic mashed potatoes with my pot roast anyway.
Worst pot roast ever - meat, potatoes, and carrots in water, with no seasonings. Blah.
