I'm aware of the rocket equation, so I don't see why you're telling me this.
Really?
This is talking about launching payloads from the earth. I'm not exactly sure what constrains are leading to that inflection point, but we're talking about a completely different issue of payloads, after assembly in LEO
You missed this bit
"The rocket equation can be applied to orbital maneuvers in order to determine how much propellant is needed to change to a particular new orbit, or to find the new orbit as the result of a particular propellant burn. When applying to orbital maneuvers, one assumes an impulsive maneuver, in which the propellant is discharged and delta-v applied instantaneously."
I guess you don't understand the rocket equation as well as you thought you did.
Your claim is that two payloads launched from earth will get to mars, but if assembled into a single payload in LEO they won't have enough fuel to get to Mars.
The fuel was enough to get them there separately. So how exactly do they need more fuel when assembled and put on a single rocket?
You appear to be misunderstanding the issue.
Launching two payloads A(X+Y) and B(X+Y) to Mars appears superficially the same as taking one of the payloads - A - splitting it into X and Y and making each of them twice as big, so 2X and 2Y, launching them separately into LEO, assembling them together on orbit A(2X+2Y) and boosting them to Mars.
The reality is that you don't get to do the on orbit assembly for free. That comes at a cost. At the very least, you will need some sort of manuevering system to carry out the task of linking these two machines (the rover and the skycrane) and if you think that will be as easy and docking them together like a capsule to the ISS, think again.
Take this rover...
...assemble it to the skycrane...
... so that it ends up looking like this...
... then insert the whole thing into its backshell, like this...
... then bolt this heat shield in place.
You have to do all this in space, with no additional equipment or resources over and above what it would have taken to launch two original sized rovers separately and send them to Mars. If you cannot do that, then your claim
"We have the equivalent of 2 perseverance missions" fails!
Now, here is the reality...
You might be able to pre-assemble items 1, 2 and 3 and launch them as one payload, but I seriously doubt it. I have watched the video and live feed of how this thing was assembled. The assembly team needs access to the top of the rover as well as both the top and the bottom of sky-crane.
However, you cannot pre-assemble items 4 and 5 and launch that as an assembly. The heat shield is mechanically attached to the back-shell but not to the rover or the sky-crane.
Now, this is not going to be able to be done by some kind of docking manuever. In order to make this work, you will need a team of perhaps four to six mission specialists. You will have to launch these guys into space to do the job, so that means a manned launch (more expense and more fuel), and then a re-entry and recovery when they are done. This assembly takes many hours of intricate, painstaking work. You might need to use the ISS as a base of operations, so that means getting into a 405 km orbit, thats higher than the one the Mars Missions do their usual TMI burn from (so more fuel expended to get your two payload launches and the assembly team to a higher orbit).
All this would just be a waste of time anyway... I have already shown that there is no way to land a 2000+ kg rover on the surface of Mars using the Skycrane/supersonic parachute EDL concept. The atmosphere is not thick enough or dense enough to allow any realistically sized parachute to arrest the entry vehicle's velocity sufficiently to land it - essentially, you will run out of room. It has already been said by the guy who actually conceived this method that these two rover missions are pushing the very edge of the capability of this landing concept. If they want to go larger, they will have to come up with something different in the same way that they came up with this method when they realised that the airbag/lithobraking EDL system had reached its mass limit.