Marksman Building?

*At least according to Kevvl: he says max SE 1 Boost > Max Boost 1 SE

Aya, that is indeed true. I'll do the math real quick, using a random damage range from damage-ranges.com
Ok, this one.

Judging by his total Dex and Attack, he has 134 W-Att.
Judging by his Minimum Range, he has 65% mastery.

With that damage range, his DPH would be 15,184 average, without any SE.
Make it max SE, and his DPH is 25,271 .18
Give him Max Boost, his range would becomes 2974~3633
That makes his average DPH 24,645 with level 1 SE.

Sure, it's a bit extreme to only have 1 SE, but it's the same idea with more. SE is a constant additive, put it on a graph, and it'll go up in damage with a very slight variation in curve when the activation % goes up.

Saph also did one.

 Spoiler

Level 133 MM: 90 STR, 687 DEX, 140 WA with elixirs (taken from Senyain's DPS comparison from April)

A: 10 SE + 30 Boost
Damage range 3139~3844; average 3491.5
%DPS: (100 + (220 * .45)) * 4 / .72 = 1105.556%
#DPS: 3491.5 * 1105.556% = 38600/s

B: 30 SE + 10 Boost
Damage range 2356~3665; average 3010.5
%DPS: (100 + (240 * .55)) * 4 / .72 = 1288.889%
#DPS: 3010.5 * 1288.889% = 38802/s

C: 10 SE + 30... Snipe?
Damage range 1995~3588; average 2791.5
%DPS: ((100 + (220 * .45)) * 52 + x) / 10.08 = 1026.587% + x/10.08
#DPS: 2791.5 * 1026.587% + x/10.08 = 28657 + x/10.08

x = 68k (Newtie's HP): 28657 + 68000/10.08 = 35403/s
x = 100k (current cap): 28657 + 100000/10.08 = 38577/s
x = 200k (JMS cap): 28657 + 200000/10.08 = 48498/s[/quote]

As to the TS's questions...

1) Not if you're poor. MM boost is a great alternative, the damage difference is fairly slight. Personally, I'm hunting Pianus daily for my SE. Failed 2 books so far ^^;
2) As the rest of my post has shown, Snipe first is great for soloing certain bosses, but practically, a bad idea. With the KMST updates, you'd even make decent exp sniping Crimson Guardians (No Strafe required, although you can bet it'd help).
[spoiler=Snipe @ CG's]

Another number crunch for you: Spamming Snipe and nothing else at CGs, level 130.

360 Snipes per hour, 1 CG per Snipe, 6200 EXP per CG.
360 * 6200 = 2,232,000 EXP/hour.
50,662,758 EXP to level from 130 -> 131.
4.24%/hour.

Eh...

With the KMST updates, we're talking "Decent"!
900 Snipes Per hour, 1 CG per Snipe, 6200 EXP per CG.
900 * 6200 = 5,580,000 EXP/hour.
50,662,758 EXP to level from 130 -> 131.
10.62% per hour.

Heh...
[/spoiler]
Pierce first is great with the Time Temple, and also pretty good if you train at Peak or Guardians.
SE first is ideal for partying, and better for DPS. Ironically, if you frequently train with an Archer that has max SE, boost is obviously better, so it's not ALWAYS best for parties!
3) You'd have to ask someone with more than level 1 Pierce.