Number of attributes a character uses

Usually just three. Max out Sword, Axe or Hammer, then Strength, then Tacts.

W/R:

9 str
9 axe/sword
Rest on wilderness

Since I got the runes etc. I need all I can get on wilderness for troll unguent and apply poison ^_^

depends on my character and their build....usually 3 but sometimes 4 (a few points into prot for my 2ndary monks helps with rebirth).

At most, 3, although I have played a couple bars with a janky 4. You really don't want any more than 3 most of the time anyway. Hell, I run 2 atts on my Warrior (14 sword, 13 str) in PvE...

depends on the build as everyone says, mostly 2-3 att lines, usualy split 12,9,9

on my sin i have 4 att lines usualy, 11 dagger 10 crit, 6 shadow, 8 earth prayers, or with grenths grasp 12 dagger, 10 crit, 4 deadly, 7? wind

It's funny when good players usually understand that energy totals don't matter over the course of battle, since energy management plays bigger role, but when it comes to choosing Elementalist attributes Energy Storage jumps to 11-13 points without question. What's up with that? I'd rather take 11 point ward on fire Elementalist bar.

I run 2 a lot. Sometimes I'll put on 3 like with primary att characters. But usually only 2 on warrior.

On my w/p I only use swords-12+1+1 and str-12+1. God-mode dragon slashers have no need for other attribute lines

2 or 3, sometimes a 4th but thats usually leftover points for things like mending touch etc.

2-4 is typical, with 2-3 being most popular. I would 3 is most popular, the 12 9 9 split. Works with almost any build.

There are some weird builds that use 5, and a few terrible ones that use 1. I don't recommend using any of the latter, however.

Mostly 2 though I run 3 sometimes.

If you play as mind blast... you want some energy so you can get it more with it.

Elementalist: 2 (one for the element and one for Energy Storage)
Monk: 2 (one for type of healing and one for Divine Favor)
Mesmer: 2 - 4 (sometimes it can't be helped to be spread across all attributes)

3 on average

It depends on the profession I'm playing and the build. Sometimes two in the profession, sometimes 3. If there are 4, its just leftover points in something.

For example, splinter barrage ranger has points in expertise, marks, and channeling, leftovers are in wilderness.

Midblast; GoLE.

Besides that, maxing energy total is really bad when you sacrifice things you should not trade for energy (HP/Armor)

Eles are fine with 12/9/9 thou. Its not like aegis/hp/wards/whatever are going to be cool when you cant reliably midblast energy to keep them up.

Seriously spec into?

Depends on profession. Usually 3
Dervish is nearly always 2 - Scythe and Mysticism. Everything else is worthless trash.

Warrior... 2 or 3 - Either full Weapon/Strength or speccing Wind Prayers/Elemental Magic.

Ele... Generally 3. There's no real reason to ever run 13 Energy Storage. Drop points from Energy into Air/Earth/monk lines/Channeling for Wards, Blinding Flash, Aegis, Splinter Weapon etc.

Monk is 3. Hybrid Prot/Heal >>>>> pure Heal or Prot.

Ranger is 3, too. Expertise/Marks/Wilderness or Expertise/Beast/Weapon, or Expertise/Marks/Channeling for Splinter Volley.

and that's all I can be bothered to remember now.

The reason many players balance their skills the way we do is because the game tends to reward that method.
It sounds a reasonable idea to split the points 50/50 between primary and secondary but you would probably be ineffective in both.

Some builds work using more points others do not, I have used a lot of secondary points in some of my ranger builds.

R/E for example where I use fire to boost damage so my points are pretty much all in Marksmanship and Fire.

or
R/Rit where I am using splinter shot and want to boost the effect of that skill.

E/M is another example you could use max points in energy storage and the rest in smiting or healing.
A Healer or smiter with 100+ energy can be pretty effective

12-12(-3)
12-11-6
12-10-8 (or 12-9-9)
11-10-10

This is all my characters:

Ranger: Marksmanship, Expertise, Wilderness survival - puts remaining into prot just for rebirth so the points aren't wasted.

Warrior: Axe mastery, tactics (moreso than strength), strength - puts remaining into prot just for rebirth so the points aren't wasted, I sometimes move from axe to sword depending on my build though I mainly use axe.

Mesmer: Domination magic and inspiration magic. Again, remaining into protection prayers.

Necromancer: Varies on build, though always have some in soul reaping.

Assassin: Dagger mastery, critical strikes, remaining into shadow arts.

Ritualist: Channelling magic, about level 9 restoration, remaining into spawning power (for when I go support and bring a spirit or two).

Dervish: Scythe mastery, then mysticism, then earth prayers.

As you can see I generally am a one-profession kind of guy, with the second profession having little use beyond a res or something.