Before moving to almost a front 4 lately, the Liverpool midfield 3 often moves from a 6 with 2 8's to 2 6's.
All depends on the team having or not having the ball.
Shaqiri getting more game has seen this change slightly but Klopp has said in interviews that the formation is not the main thing for him. Players taking responsibility and understanding the team responsibility in both covering or creating space seems paramount. We rarely see what is referred to as a double-pivot in truth. Possibly with Hendo & Gini, but mostly it's almost been a triple. Something maybe seen previously in Mourinho teams. Where one player does a lot of the covering and the "double-pivot" is higher up the pitch. It will be interesting to see how that evolves with Shaqiri forcing his way into the team, or will it become increasingly more like a 1-4-2-3-1, especially with Ox coming back.
Edit: Moving to a midfield duo, doesn't necessarily mean the team will move to a double-pivot.
Yes, pretty much mirrors my thinking.
As regards the alleged "double pivot", I think what we see is much more similar to the "volante" system, because the focus is on control rather than defense.
Interesting point about a "triple pivot", or what I have been calling a "staggered 3" in midfield, and the possibility of moving away from that to a more structured system in order to accommodate Shaqiri, a player who we both gain and lose from when he plays.
My own thinking is that as Shaqiri becomes better at defending, or more precisely, recognising when to defend, we'll start to see Firmino back as the primary/secondary attacker.
What I see at the moment is Firmino dropping ever deeper to help take up the slack from Shaqiri's relatively poor defensive work.
I say "relatively" because Ox is so much better at that side of the game, but in fairness, he's had a lot more practice.
The possible midfield duo won't change much I don't think, as they are primarily defenders, and an interchangeable "volante" (I know it's not an exact description, but it's the nearest I can get with one or two words, so I just use it more for the purposes of illustrating a point, rather than saying we are actually playing that system).
I think we'll still see the 2 guarding the flanks predominantly, rather than the centre, and I think the reason for this is the pace we now have in both CB's negates the need to split them, and move wide to cover behind the FB's.
It's wonderful how Klopp has us playing, and I think it is only going to get more complex, as players become adept at switching between various scenario's.