Yes, it would be. Since the odds of getting a shiny Pokemon in gen IV is a 1/8192, or a .01220703%; .012% rounded. So, it's not a lot. Since you are encountering 3 Pokemon at the same time, each has that 1/8192 chance, so It'd be a 3/8192, or a .0366% for each soft reset. And sadly, no, percentages and probabilities are different. Say you have 1/8192 for a shiny. You could SR 10,000 times and still not have it shiny, because each encounter has the 1/8192. I did Lugia in SS, didn't, get it until 12,777 SR's.

Good luck on your hunt!

I'm on 700 for starter in HG.

Happy Shiny hunting,

~Freezee