10% is barely anything, and that's why I stated directly "it isn't a big deal". But you also have to remember that this game is looked to as an MMO, not a single player hand-held game.
I recall another issue the game has with a queue of 1,000. Excluding the numbers you generally have online, because I don't know an exact for it, let's use the 1,000 for the calculations.
That means in every 8 battles, you get 1 shiny. That's assuming there's only 1,000 players and that they only do 8 battles a day.
So not only do I think lowering the shiny rate is a bad thing, I wouldn't complain if they devs INCREASED it.
Now this is breaking from single fun into a more MMO community, but you need to look at a few factors in all of this. So I'm not going to go any further into it, as I'm sure there's a handful of people who want me beheaded for even suggesting a decrease in shiny appearance rates.
But what you have to realize is this game lacks an end game. Once you get so far you're stuck with the VS seeker and a Pokedex. I would bet money that people get on this game simply to find Shiny Pokemon and I think it's very unfair to belittle their efforts EVEN IF by a small percentage chance for other players.