I'm sorry for your loss and I know you must feel awful.
But accidents happen anywhere. Not just in paddocks but in stalls, leading around anywhere. My friend had a quiet horse and she was leading her one day and she spooked, reared, flipped and died. Stuff just happens.
Two accidents in several years... it's unlucky but just that.
My personal opinion is horses are happier in paddocks with other horses and its my preference to keep them in that situation. And yes they get injured sometimes but, as said before, you can't wrap your horse in cotton wool. It'd be like never going in a car incase you have an accident. As long as the paddock is safe and not over-crowded then I don't think there is really a reason not to use it. I think horses are happier in them, and if it comes with a little more risk, I think I'd go with that an quality of life.
My horse is currently kept in a small paddock alone and she is miserable and it makes me sad everyday. I'd love the opportunity to put her in a big paddock with horses, and I'm trying to make it happen.
I hope you feel better soon, and again, I'm sorry.