Slow Cooker Pot Roast

I did something wrong here.  5,105 people have given this recipe an average rating of 4.5 stars.  They rave about it!  It's moist, it's delicious, it's AMAZING!!!!

My meat was tough and the gravy thin and flat.  Where did I go wrong?!  I only tweaked the recipe a tiny bit, and in ways the 5,105 reviewers had suggested!  I'm going to have to try this again.  It certainly wasn't bad, but it certainly wasn't awesome.

2 cans condensed cream of mushroom soup (I used the low fat ones)
1 package of beefy onion soup mix
1 1/4 cups of water
5 1/2 pound pot roast
baby carrots
pearl onions
baby potatoes (reds, yellows, fingerlings, anything small and waxy so you don't have to worry about peeling)
button mushrooms
flour
salt
pepper
seasoning salt or garli garni
optional: Marsala

Season your flour with salt, pepper and seasoning.  Dredge the roast in the flour to get all sides coated.  Sear in a pan over high heat.
In the meantime, mix the mushroom soup, dry soup mix and water in your crockpot.
Once the meat is seared on all sides, put it in the pot.
Cook on high for 3-4 hours or low for 8-9 hours.
One hour before it's done, add your veggies and allow them to cook along with the meat.

This is where I'll try things differently - I cooked my roast for 5 hours on high; next time I'm going to try the 8 hours on low.
My gravy was a bit thin, so I ladled some out into a pan to thicken up.  I added a little bit of a slurry of flour and Marsala to flavor it up a bit as well since it tasted a bit flat to me.

Overall it was good, but not nearly as richly flavored as I had imagined.  What a let down.