You really need to try to make the effort to apply it correctly. Applying it the way you are might do some damage to tender roots, or to soil critters, and is not likely to get the product where you want it.

If Miracle-Gro isn't convenient for you, you might investigate a good granular fertilizer that is manufactured to be broad cast over the soil and watered in.

Probably you'll overapply Miracle-Gro if you do it that way....I know I do.

Here is a link that might be useful: Garden Musings

If you haven't had any problems so far, then you are doing fine and can continue. Just watch the amount you are applying and frequency and gauge that against how much of the diluted mix you would apply. You could apply it too heavily, but otherwise you would be just fine. The granular fertilizers dissolve the same as the miracle grow crystals, except for the clay carrier, but they don't dissolve as quickly as the crystals do.

Old farmers once used some contraption that attached to their cultivator which added some dry granular fertilize to the soil after tilling the soil to remove weeds. So the concept of not diluting the solid fertilizer was once used. I don't know about Miracle Gro but I don't see as how it could be strikingly different.