I'm not sure what you mean by guessing game. The items I make have a green text below the item description (when in reverse engineering mode) saying I have a 20% chance to learn a new schematic. When there is no new item to be learned, the text is red and says so.
You misunderstand. In order for me to even find out if I can Reverse Engineer these items, I must first take 20 Black Hole Comms, buy the Schematic. Once I buy the Schematic I have to find the Mats to create the Exotechs...which costs a ton of cash. Then I have to sit for 45 minutes while they are being crafted. Only when they are finished being crafted, after wasting time, credits and black hole comms, can I learn if they can be Reverse Engineered.