Maybe I'm misreading something, but Glitchs are not failures, they are unforeseem circunstances or small problems with your action, you are still successful (unless it is a critical glitch). Based on most examples from the book, a glitch is something like a -2 modifier to your next test, or something like that. So it is not anything major. It is definitly nothing life threatning, or game changing. Now, a critical glitch is supposed to be life threating (but still capable of being dealt with).
Also, Edge can be used to downgrade a critical glitch to a regular glitch or to negate a glitch, so again, a glitch is easily avoidable.
Now on statement that they happen enough with massive pools, I find that quite impossible, since a glitch has less than 1% chance of happening with a pool of 6 dice (with 7 it bumps to 1.7% and then drops again to 0.46% with 8 dice), and less than 0.1% by 14 size pool, this is effectively never.
Critical glitches are even worse, you have 2.8% with 2 dice and around 5% odds with 3 dice, but then it drops to 1% and by 6 dice it is below 0.5%, by 10 dice it is below 0.1%.
So, with a dicepool of 6 dice, you have 1 chance in 100 of having a glitch, and 1 chance in 200 of having a critical glitch, any pool size above goes even lower much more quickly. With a pool of 12 (nothing extraordinary, not even for new characters) you have about 1 glitch every 800 tests, and 1 critical in 6.000 (SIX THOUSANDS) tests!!!
Also, I still think that the chance of glitches should diminish with how high are your pool size, but it shouldn't disapear neither they should be so rare that you never even remember them, after all you have Edge to deal with them if you need (and the book says so right up front).
Even if you are an expert marskman, something wrong might still happen. A change in the wind, a shout in the distance, or something else that doesn't fail your shot, but make it not happen as you would like. And if this something wrong DOES happen you are an expert and probably quite capable to deal with that easily. This is how I understand glitches...