I agree the Ryuken HRL has primarily ARO utility but no one should fall for that. Edit: although "you should never reveal in ARO" is also usually true, unless your opponent makes a big mistake.
I think marker state AROs are good for what the prevent more than what they do. A piece with a good chance of winning a face to face roll with another might be discouraged from taking the shot if it also means potentially eating an ARO from a marker. Forcing your opponent to split their burst can be an effective tool for discouraging aggressive moves.
You'd be surprised what kind of guessing game you can play with the mine. I disagree about the "Never reveal in ARO" for limited camo - without Hidden Deployment your opponent can already interact with you on his own terms.
That's why you usually don't reveal, why would they give you a good shot? Unless your shot is more likely to cancel the shot than the discover, but that's uncommon. If they discover on 10 (MSV2 WIP 13) that's a 50% chance to survive before ARM. Your shot back, assuming no penalties over cover, will have 12 successes. Their highest number rolled for you to have a 50% chance to cancel is 2. Of course you can factor in canceling some of the shots but not all, and that a success with the HRL is better than them failing discover. But the nature of Infinity makes it hard to scratchpaper the numbers. As a general rule of thumb simply not revealing is a good standard until you pick up exceptions.