200 meters might simply be the maximum distance at which a human can accurately aim an ideal, recoil-free, ballistics-free pistol. A two-hand-hold might increase the range slightly; a bipod or other support, combined with a sighting device, would increase it basically all the way to the horizon.
Of course, with a beam weapon, one should be able to walk the beam to the target. So even a phaser pistol would hit the enemy guard eventually even if he stood two kilometers away. But apparently hand phasers can't sustain a beam for very long - and for some reason, walking the beam is basically never done.
My favorite phaser is the ST5/6 "assault phaser", as long as it really is of a special type separate from the usual sidearms. I could see it as Starfleet's Thompson SMG: a firepower multiplier specifically designed for starship use, just like the Tommy gun was a Navy security and boarding party weapon first and foremost. If it's just a standard phaser in jazzier covers, it becomes sort of silly.
A range of guns would make sense... The two-piece sidearms of TOS and ST3 would be somewhat sub-optimal in terms of firepower and optional extras, but compact and versatile and thus specifically suited for use by starship crews. Real weapons of war would be larger, because state of 23rd century (or 24th century) art wouldn't allow for miniaturization of the crucial functions (autotargeting, stabilizing) below the "rifle" size. A happy medium might be struck with the ST5 phaser, which would be primarily used when knowingly going to infantry-style combat.
Since we have some evidence of such a range in TOS and TNG alike, it would be fun to postulate the "missing" pieces for the other eras. An early TNG rifle, or a TOS movie era one, or a "The Cage" era "submachine gun"...
Timo Saloniemi