What's the logic behind Archer shots causing Entanglement?
It is both plausible (Entangle is a Level 1 Druid spell, so Archers have easy access to it) and desirable, as it prevents the victim from closing to melee range. Note that I'm not implying that the arrow (or whatever projectile) is actually dragging the physical vines behind it--it is simply an extension of the Archer's will, and so a relatively simple ability like Entangle is able to ride piggyback.
The story is similar with the Sniper's (Improved) Invisibility, it mirrors something that the class could already do, even at low levels. Granted, the roleplay could be easily abused--my "approach stealthily, fire a shot, duck back under cover" story makes sense, but the ability could just as easily be used by a Sniper who got caught by the guards: "You can see me, so I can't drop back into Stealth and escape, but if I shoot you, maybe I'll disappear!" So there is definitely
that flaw. But then again, Stealth
itself is flawed, what with how you only need to be out of sight for a split second in order to vanish completely, after which you can dance around for hours in well-lit, perfectly bare rooms, surrounded by enemies, while remaining completely (yet somehow non-magically) invisible. So, truth be told, I'm not too concerned that the Sniper's Called Shot isn't entirely realistic. Granted, there may be better alternatives, and please do suggest any that seem plausible. When I first came up with the Sharpshooter (as it was called then), Andyr suggested adding Poison damage, but I decided against this as there are already a wealth of elemental-damage projectiles, and Poison is already the domain of the Assassin.
The Visual Range ploy is very interesting, thanks! I don't think it will really fit with the Sniper, though, as it would require him to deploy an invisible scout (
a la a Wizard Eye or Familiar) to spot for him--either that or just start lobbing projectiles at enemies he can't even see yet, which of course makes no sense at all. Besides, shooting at targets that you cannot see is more of a Zen archery trick, so given the option, I'd like to save this for my future experiements with Monk kits.