First and foremost, did you check that wayfarer doesn't start with the Scientist talent? It gives +1 bonus in Blacksmith and Crafting, it doesn't give free attribute points.
Now let's take a look at what each stat impacts (I'm quoting divinity's wiki here):
Strength
Boosts Man-at-Arms skills
+20 Weight per point (base 10)
+6 Offense Rating per point for Strength-based Weapons
Dexterity
Boosts Expert Marksman skills
Boosts Scoundrel skills
+5 Defense rating per point above 5? (base 4xLevel)
+6 Offense Rating per point for Dexterity-Based Weapons
Intelligence
Boosts Elemental skills (Aerotheurge, Geomancer, Hydrosophist, Pyrokinetic)
Boosts Witchcraft skills
Every 2 intelligence points after 4 int reduces the cooldown of magic school skills by 1 turn
+6 Offense Rating per point for Intelligence-Based Weapons
Constitution
+1 Maximum Action Points per point (base 7)
+10 Vitality per point(?)
Speed
+0.1 Movement per point
+0.5 Initiative per point
+0.5 Start Action Points per point (base 2)
+0.5 Turn Action Points per point (base 3.5)
Perception
+1.0 Hearing per point
+0.5 Initiative per point
+0.5 Start Action Points per point (base 2)
+2% Critical Chance per point above 5
Ability to detect traps
Accuracy when shooting over distances
Every 0.2 meters from the target reduces chance to hit by 1%
Each point of Perception increases the distance before penalties due to range take effect by 0.4 meters.
Now that we saw what each attribute does, let's ask ourselves some questions:
Do you want to use weapons to attack or magic?
If you do want to use weapons, you want to use bows/crossbows? If you do, you will have to invest in dexterity and perception. And you will want to max Expert Marksman to get the talent Quickdraw which lets you attack with a bow using the same amount of ap that a 1-handed weapon uses.
If you want to use magic, you can ignore dexterity and str and will want to raise intelligence a lot, but you will still want to have good perception to detect things (I've read here that 14 perception is able to detect everything).
Constitution is mandatory since you're planning to use Glass Cannon, so we can't ignore that, at least 4-5 points will go into this attribute.
Maybe you could get Light Step to reduce the need of perception (it gives 2 bonus to detect traps and secrets, which means you need to spend 2 less attribute points in it).
Speed you can get away with speed 7 or 9 (Glass Cannon will give you a crapload of AP, so you don't need to spend too much here).
Finally, equipment. You can find lots of equipments to boost attributes on vendors or from looting.
Crafting can also help you a lot this regard.
If you don't plan on using Lone Wolf, turn Jahan into a crafter. He starts with Scientist and you only need to reach 3 in Blacksmith and 3 in Crafting (get to 5 using bracers and belts).
Buy every Tormented soul you can find, and craft it onto your weapons. Initially it gives +1 str and +1 dex, but later (lvl 14 if i remember it right) in the game the bonus doubles.
He can craft a belt and an amulet with a Magic Claw to get constitution bonus.
He can craft a Lucky Rabbit Paw Super Ring to get +1 Speed and +Movement.
I hope this helps. Also, stay tuned, more people will probably answer this.