I wouldn't go that far. Melee advantage when your charisma based and aren't causing it yourself isn't common in my games. Spells or prone are typically the only way to proc it and even then most of the better combat spells don't cause it. If anything you'll be likely to have it in easy fights and less likely to have it in hard fights IMO - which is the exact opposite of what you would prefer.
Depends on party composition, really. We had an open hand monk in the party, so prone and stunned enemies were extremely common. And it would be more common on boss fights, since the monk would burn 5 ki a round if necessary to get the stun to stick.
In the right party though it can be devastating, as some partys nearly always generate advantage - though it's still costing those other PC's resources to generate said advantage that they may could have used to do something just as effective. Anyways, at this point you need presumably 3 feats, which means by level 12 you've still not maxed your charisma and so you pretty much suck when you don't have advantage (because 16 cha isn't really enough to make use of the -5/+10 feature against most enemies). It also means you didn't take the actor feat (or if you did then you did so at the expense of those other feats or your charisma).
Personally, I only took EA and GWM. PAM is a boost, of course, but I found triple advantage attacks, especially combined with hexblade curse, caused enough crits and takedowns to fill up a large number of available bonus actions. And as others mentioned, EA gives you a level 4 Cha 18 that's useful for both melee attacks and
eldritch blast.
How though? If you really took elven accuracy, GWM and polearm mastery and the extra attack invocation and the invocation that lets you use a great weapon with the hexblade ability. you presumably only have 16 cha, 2-3 invocation slots open (1 for most of the game), no notable out of combat abilities etc.
Pact of the Blade lets you use great weapons with Hexblade, no invocation needed. Invocations are a little tight, but as you mentioned above, none of them are so amazing that they're must takes. I had AB, the extra attack one, the one that treats your weapon as a +1 (because when the game ended at 11 I still had never found a magic weapon, lol), Tomb of Levistus, and Devil Sight.
I guess you have 2-3 short rest recharging spells per day. What are you using them for?
Whatever's needed, really. AoA against weaker minions where it should proc a couple of times before going down. SoM if I really needed some defense and advantage. Synaptic static or thunder leap if I needed AoE. Counterspell, of course. I had a few other spells (hypnotic pattern, enemies abound, some other filler), but they came up fairly infrequently.
I really don't see what he's doing at a B+ level besides melee when allies grace you with advantage.
Depends on your metrics, I guess.
