I know you have stated you are not taking feedback from me again for one reason or another, but gosh darn it, I'm giving it anyways.
How many people where in your test? (Bots don't count)
Where in the map is this spot? Near spawns, between mid and spawn, or just mid?
1. If around spawn/between spawn and mid: Usually, if the engie is going to set up at said stop early, when no enemies are around (easiest way to do it), they basically becomes useless until the sentry range is reached (this is assuming that this spot is near the spawns) and so really I would consider it balanced, he's sacrificing his sentry during early/mid game to have a strong defense (even though it is a bit open)... even though he's making himself SEMI-useless during early/mid game.
2. If at mid: If the engie can get through the fighting around mid and somehow manage to get a sentry up and then properly wrangle himself up to this spot without dieing or drawing attention to himself, then I'd also call it balanced because the opposing team is blind, or the engineer is RIDICULOUSLY good.
3. If at mid, but there is no fighting, see 1.
From the way you are describing it in the post, I'm going to assume that #1 will apply.
Take that all as you will.