First thing first. You must understand 2 things about the 2h warrior in DA I:
1) Outside of Reaver, the damage is purely based on knockdown or stunning. You're more of a control/damage-based class this time around.
2) You can't survive. Don't try to tank. Don't.
Here is what I would recommend. It's pretty much a no-specialization build until near 20, at which you can move down Templar if you so wish.
Note: You can knock out a few levels with extra ability points. if you are human, you also got 1 extra point!
4 points - Level 3: Mighty Blow + Upgrade [Two-Handed Weapon, Right Side] --> Gappling Chain + Upgrade [Battlemaster]
3 points - Level 6: Block and Slash --> Flow of Battle --> Pommel Strike [Two Handed Weapon, Left side]
3 points - Level 9: Crippling Blow --> Combat Roll --> Coupe De Grace [Battlemaster, Left side]
3 points - Level 12: War Cry --> Charging Bull + Upgrade [Vanguard]
1 point - Level 13: Shield-Breaker [Two- Handed Weapon, Right Side]
Choose between:
1) 1 point - level 15: Horn of Valor + upgrade [Battlemaster, Left side]
or
2) 3 points - level 16: Hamstring --> Deep Reserve --> War Horn [Battlemaster, Right side)
or
3) 4 points - level 17: Payback Strike --> Turn the Bolt --> Lunge and Slash --> Turn the Blade
It depends whether you want to have a AoE CC, or a team buff or survivability. You could also go down Whirlwind, but that's only if you plan on slaying some dragons! From here on you can either take the options you did not choose, or go down Templar. If you really want damage, you better reload an old save and go Reaver though.
Forget about Templar for now. It gives you nothing of value at this point
Spell Purge? Useful, but situational. Good for combos and mages!
Champions of the just? The hardest enemies in this game aren't demons! So this is very situational
The last sacrifice? If your goal is to die, you are doing something terribly wrong!
Blessed Blade? Useful, but limited.
Maker's Will? 5% chance is.. not very good.
There is no Darkness? Won't increase your damage at all.
Wrath of Heaven? Very good, but heavy into Templar.
So, your best bet is to build out just build before touching Templar. It can be the icing on the cake -- it can't be a part of the core build. Sadly. Until they give templar a huge magic resistance passive, it's a subpar specialization. Especially as a 2 handed warrior. It wor