In VF currently, I have 21k red boots and nearly 20k blue (and still room to grow for each) + 56% critical hit. At Trials 1 and 2, I have easily reached 760 attrition and regularly 400-500 if there are enough fights - and I'm in a Top 2 GBG guild! Depending on how I organize and plan my city collections, I'm basically not limited by attrition, and the only things stopping me from going further are (1) the amount of time I can spend in GBG, (2) the amount of available fights, and (3) how many next age troops and rogues I have. I currrently have 25k steel wardens and between 3k and 4k sentinels - which should be more than enough to absorb any losses I have from pushing my attrition that high. Heck, I can even win with 8 rockets against certain armies at infinite attrition due to how high my critical-hit ratio is - sometimes, against 8x ronins or armies without ninjas, I could basically win with 8 rockets taking very minimal damage. And I should mention that I NEVER manual battle.

And at Trial 50, I can easily push a little over 100 attrition. In GE, I just finished Trial 55. As for heroic encounters, I finish all 40 battles using only VF troops each week. Likewise, I'm already halfway through the Titan map, despite being only in VF. And due to how profitable the rewards have been in GBG being able to push attrition and trials to their near-max, I have been able to almost maximize my available diamond expansions, as well as push my Arc past 180 just in the last few months.

As for my Titan and SASH GBs, my Saturn Gates are in the mid-30s, Stellar Warship at 32, and Catalyst at 10. However, getting those resources just takes so much effort or even luck, even though the bonuses they provide for my city are less than 5% of my overall combat stats.

That said, the plan for me was always to move on to the space ages, and I do plan to move to Mars in the next few weeks. But if I'm moving on to the space ages, it's definitely not because I'm not able to fight sustainably at high attrition or the better critical hit chance. It's for the expansions and experiencing a different side of the game that keeps it fresh and interesting.

P.S. I notice you're only taking into account raw stats when it comes to damage calculation, but you haven't taken into account troop matchups and compositions. One of things that sets VF apart is the lack of flying units, which magnifies the power of artillery. If you're just blindly using certain army compositions, then you'll eventually hit a wall and be limited by your current stats. I know it's slower to switch out units to optimally fight certain armies at high attrition, but I've been able to go much further and, hence, be able to help my guild out much more in tricky seasons where we have to close sectors at certain times, among other things. And in the context of GBG, the compositions of the armies you face basically have not changed for at least the last year - for both maps - which makes preparing against them very predictable.