Being able to beat the cube is an important part of your setup now. If you cannot, then you will not get far.
Let's start here. The Cube is extremely dangerous, and the stuff it can throw at you can and will bring you down. But there is one massive flaw with the cube.
It is slow. On Round 3 will you get the Improbability Field, by which time most PVP fights will have been decided. If you get hit by Atom Smasher, you will survive and hit back, or you had already lost.
It has no actual offensive capability until then, and no direct damage until Round 4. The first 2 are basically damage mitigation, which is bad, but not problematic if handled well. The same goes for Reality Hacking. Knowing this doesn't really help of course, given the agent is sure to have something else equipped as well. But it is better than worrying specifically about the Cube every time you see it.
Reality Hacking is a passive Avoidance effect fixed at 20%. In the short term, it can be as high as 90% or as low as 1%, but in the long term, across everybody's experiences, 20%. It's far and away the biggest obstacle to beating the cube.
It's not immediately obvious what can bypass this, but once you know, it is fairly easy to determine.(Scrappers) and (Tactician's Power Armor).
This is highly dependent on the opponent running an infiltrator, but from what I've seen this season, that should not be a massive problem.
The next most obvious, this also ignores Reality Hacking and has pretty much 100% chance to hit.
My absolute recommendation for this path is Modern Armor Thor. Nobody else hits as hard as he does, with the possible exception of Hulk. His L9 can easily take off 1/3rd of the opponent's health, and with extra turns he will quite happily do more.
This is better than True Strike, but more difficult to get your hands on.
Much less common in today's meta, and possibly more difficult to use compared to Ethereal Strike. If you have Phoenix Five Phoenix, her passive can randomly grant any member of your team the ability to bypass Reality Hacking.
I have no real recommendations for this, as this largely revolves around 1 or 2 heroes, and I personally wouldn't advise this path for the time being.
Up the Overall Number of Attacks
This is by far the most straightforward method. It'll only proc 20% of the time on average, so up your number of attacks to 125% (Math - 0.8*1.25 = 1).
But seriously, the more the merrier. Counter Attacks, Follow-Up Attacks, Extra Turns, anything that increases your total damage output will increase your final damage output.
A milder point is that Attack Stat increases will do the same thing in the long run, but to a lesser extent. I've seen people using Scrapper World War Hulk on defense for this reason.
How do we get around this?
Well, the most straightforward answer is Area Attacks. Disoriented does not proc on Area Attacks :P
I am also lead to believe that Disoriented is an Avoidance Effect, so anything I listed against the Reality Hacking passive should work. Correct me if I am wrong on this, I have not tested it completely.
The Light Fantastic
It cannot be removed by Scroll of Angolob. So don't try. I know that if you have your own Cube, then you can use your own Blackest Void to send it packing.
Normally I will hit with a weak Area Attack (Cable's TO-Overdrive L2 is perfect for this), and then carry on steamrolling them.
If it comes down to it, often your only option is to up the number of attacks to compensate (but don't do follow-ups, apparently Mirror Reality will persist until the series of attacks is finished)
Improbability FieldIt's like . But more dangerous.
Scroll of Bologna if you still haven't used it. By this point the match will have probably been decided anyway. Counter with your own Cube to mitigate some of the debuffs.
It's Catastrophic. So when it hits you and you haven't recovered from the L6, you're in serious trouble if you haven't lost already. If you don't have any debuffs, or at least very few, it'll deal around the amount of a PFire, which is down to your bonuses.Bonus points if you can use on this.
My points on Improbability Field and Atom Smasher were very short. In my experience if your opponent gets to those to it will come down to dumb luck or PVP bonuses, neither of which I can help you with.
Your main problem lies in dealing with the first 2 moves and the passive. Most PVP matches will be decided by Round 3.
Always bear in mind, however, it's not just the cube you need to be able to take on. Often I've been able to take down the agent, only to find the heroes that are left are surprisingly difficult to defeat.
As for myself, I'm running Blaster Modern Thor and Cable, with Inf Agent Tank (Cube, Mystic, Attilan Guardian and Protector). Use Cable's L9 on Thor to give him 2 Turns on Round 1, use L9 on first turn, L6-L9 on second turn, and you will leave the opponent severely crippled for stomping in Round 2. Cable has the Phased Frequencies EISO, but I do not rely on Thor's L1 or L2, so it isn't necessary for him. He's not even L13 yet anyway.
Good Luck, and Crush those Cubes!