Toasting followed by blooming would not make spices "more potent" than either toasting or blooming alone, but would make them taste different.
Per Serious Eats:
Frying spices in oil gives them a completely different flavor than dry-roasting. When dry-roasted, a spice's flavor changes in fundamental ways: volatile aromatics begin to cook off, while compounds in the spice recombine to form new flavors that are often deeper, roasted, and earthier. Frying them in oil, on the other hand, tends to enhance the original flavors of a spice, making them bolder and more intense, almost as if they've become more sure of themselves. In short, oil-fried spices have a brighter and fresher aroma compared to dry-roasted spices.
For this reason, you might use spices that are dry-roasted but not fried, spices that are fried but not roasted, or even spices that are roasted and fried. In the last case, you're trying to spread the nuttier/earthier flavor of the roasted spice through more of the dish by infusing the oil.
There's a caveat, though, which is that spices that have already been roasted will burn much faster than raw spices, particularly if they've been ground. As such, you'll want to add them to less hot oil, or to oil that already has other things in it bringing the temperature down (like chopped onions).