Well no, magnetrons don't produce more concentrated beams than IR...
Lasers can cause instant blindness due to vaporizing the retina in spots, but magnetrons certainly won't do the same. If you're in a field intense enough to do that (say a military radar), you're damn well going to feel it on the rest of your body, and run the fuck out of there because it feels like being roasted alive (which is what's happening)!
Eyes are basically water, about 8 mL worth. Which might be damaged quickly by a modest 5C temp rise, which will take 170 J, or over 1kW actually absorbed by the eye and nothing else to cook it in "a fraction of a second" (which is still considerably longer than 'instantaneous', but I'll give this one for human terms of 'instantaneous'). Which would be an impressive feat, in the middle of a face, for a microwave field no more energetic than 1kW.
I don't suggest pointing the magnetron antenna tip at your eyeballs, but I don't find common magnetrons themselves to be a special concern around things made of meat (except for long exposure).
Tim