So... The Abrams tanks have absolutely nothing to do with the point being made. The engineers work would be exactly the same if the tanks weren't there.
I care not for your analysis of my tactical acumen, because I found and dealt with the mines, and apparently you were unable to do so.
How can you 'Mark Mines' if you haven't detected them yet?
What game in existence allows you to activate a context-sensitive command when the context necessary for that command is nonexistent?
Notice how no one is complaining about their inability to 'Acquire' weapons and ammo out of thin air?
That's because it's self-evident one must be in a vehicle or next to an ammo dump to use it. WHY ARE PEOPLE MAKING AN ASSUMPTION THAT 'MARK MINES' WORKS DIFFERENTLY?
You have to be standing near the mines to have it work, and in order to stand near the mines, YOU HAVE TO KNOW WHERE THEY ARE. The manual also makes it explicit that anti-tank mines do not harm infantry, so you can draw the logical conclusion that having infantry walk around and among the AT Mines will allow you to detect them without any possible risk.
I would say the scenario is designed to hold your hand by telling you where the evil scary minefield is, and also give you all the tools you need to overcome the obstacle. Imagine for a moment the anguish you would feel, if the game DIDN'T tell you there was a minefield there!
If there is any problem with marking mines, it is the ambiguous wording in the engine manual which makes it seem like 'Mark Mines' is a movement command, but by referencing the bolded spots of the game manual section quoted above (emphasis mine), one can easily see the technique by which one detects and marks an anti-tank minefield:
Anti-tank mines cannot be set off by infantry on foot,
Troops moving through minefields have some ability to notice the mines without exploding them.
Engineers have the ability to mark known minefields.
See? It's as easy as 1, 2, 3.
Now just wait until you get to a scenario where you are told, "There may be some minefields somewhere," but are NOT told where they are, what type they are, or how large they are...