I would posit that the recent UA Sword Patron is at least a partial do over for the blade'lock. While admittedly not fine tuned (Not to mention a kind of silly patron), look at all the gish-enhancing abilities it gets right off the bat to help it fulfill that role.
I think the hexblade patron pretty much shows the basic issue here. Would you ever take it and
not be a blade pact warlock? No! It makes
no sense! The pact is supposed to be a minor twist on the base archetypes, but one of the three pacts is something that
needs to be an archetype itself. The problem is, that makes no sense as long as your archetypes are based on patrons instead. The 'weight' of your archetype choice is your patron. Then we go and contradict that with something that's
almost a ribbon. In fact, you could
easily made a blastlock who happened to be a blade pact.
I'd actually posit that either Pact of the Blade was a mistake from day one,
or the overall design for warlocks got messed up and needs re-addressing. Too much weight is on the patron, and not
nearly enough is on the pacts.
If I were going to do a rebuild, I'd probably split the class clean in twain.
Level 1, Choose your archetype.
Level 3, Choose your pact.
Level 6, Pact feature.
Level 10, Patron feature.
Level 14, Pact feature.
As far as pact goes, well, blade warlocks would obviously gain multiattack at 6 and lifedrinker at 14. Chain warlocks could gain their improved pet at 6, and at-will hold monster at 14. Those work out
great. The only pact that would be an issue is Tome, it would get ritual casting at 6 and... something at 14. Maybe the ability to fuel those rituals with a warlock spell slot if they prefer?
The underlying archetypes might need some re-working -- losing create thrall and hurl through hell are some major losses for the fiend and GOO pacts, with major flavor loss -- but I think with time and effort that could have gotten buffed out.
Unfortunately, it's far too late for that to be put into the book, and I'm still feeling my way into homebrewing and no where
near ready to try and do that major a rebuild!