We like to think there's many random rolls when we can't figure out the pattern, but reactions is one of those things that are absolutely not random.
The UFOpedia has a
good article which details how reaction fire works. It's a good place to learn instead of trying to rediscover the mechanics. As far as I can tell, it already works as well as it can and is a great system to make a turn based game more dynamic.
The instances of enemies shooting many times at you probably occurred on very low reactions soldiers. 95% (from having spent 4 of 80 TUs by taking one step) of 10 reactions, still means a "reaction score" of merely 9 (integer math round down). In XCOM the aliens have really high reactions (to compensate for the AI not using squad tactics) and can shoot at you with a reaction score of 11 from, say, 20% TUs left with reactions 55, meaning they will have no TUs left after shooting. Or if they had 100% and that was your first step off the skyranger, they'll shoot many times.
It's annoying, but it "works as intended". I was toying with the idea of making snap shots half as accurate, but half as expensive, to try to reduce the number of hits from them as a compensation. Some things (cyberdiscs on higher difficulties) have almost 100% to hit with a snapshot and it becomes ridiculous.