You dont need to shatter excessivly depending on your build, you shatter tactially when you need a bit of burst, or survival. Keep you clones up if you can, you never want to be without for long as it provides distraction, shatter options and depending on traits, passive bonuses to dmg and survial and speed, also bleeding effects if traited that way.
You want to get your conditions up and working, a mesmer can keep conditions up easy and keep boons on themself, and this really has a massive impact on a fight. And phantasms do a load of dmg and are really quite durable.
I'd advise the opposite to you, dont shatter all the time, shatter when you need to, but dont just go for the CD shatter its a massive waste.
Shattering does more damage than phantasms though, but basically just spawn illusions/phantasms and when your cooldowns are done and you can spawn 2 or 3 more you shatter, eventually you'll find a rotation that has nice timings.
As for pure ranged DPS I wouldn't recommend mesmer, it doesn't really do that much damage compared to ranger/warrior/thiefs.