Is this a common thing for tanks to do?

[bounddreamer]

For big pulls, for the most part it is resource inefficient to tag every mob along the way.

For the most part, absolutely. OP is talking about a very specific pull, the AK Hard pull. It's five mobs to pull the first section of trash under a vine. Five tomahawks, shield lobs, or unmends (followed by blood price) is not too much to ensure you secure ALL the initial aggro from those very hard hitting mobs.