Good advice, thank you. I looked at GWM and if this was going further than level 10, I'd get it at Warlock 12. GWF seemed a little weak. I see its potential is good, but its not always going to increase damage. I liked the flexibility of Dueling applying to 1H weapons and 1H staff, and extra AC from a shield, although I realize getting hit can be good with damage reflection buffs. And I suppose if Hex and Armor of Agathys are mainstays, that they can be cast before combats or maintained for awhile. And even the loss of AoA/reaction attacks for one round while a 2H weapon is in one hand to cast most spells isn't that bad (lack of Warcaster).
I definitely see the value of GWF/GWM (+ Darkness optional) and its a less feat-intensive way to go about making a BladeLock, which with a low level cap is probably the better way to go. I kind of consider Darkness a cheese tactic and am sure my party won't like it, but I can see pulling it out for emergencies or times when I can draw opponents off a little to fight me away from the group. 1/day its free for being a Tiefling, so I hadn't considered adding it to the spell list at this lower level range.
My thought for any combat where opponents aren't right on top of us at the start (level 7+) is:
Hex/EB & move up next to the PLD. If he's already engaged, Repelling Blast can knockback. Then when the thing moves back at us I get a PAM reaction AoO, and on my next turn Attack x2 and bonus attack from PAM.
EB 2d10+6 + 2d6 from Hex.
1H staff'd be doing 1d6 +5, 1d6+5, 1d4+5, and 3d6 from Hex if everything hits. Its a lot of attacks and compounding of Hex.
I do lose that bonus attack sometimes when I shift Hex, so more points for GWF/GWM fitting with Hex better.
I see the level 6 Pact boon Dark One's Own Luck and it makes me think of Matrim Cauthon from The Wheel of Time books, which further compels me to want to make use of a staff and/or glaive. However, I may follow your advice and take up a greatsword instead.