Have more then 350k+ tracked tt with lvl 7 ul at 85% constant tt return. No multi's no nothing. Also i reason i sold the lvl 7 and semi downgraded mining.
However, two things
1. You are focusing on markup, which is what i did as well and that affects the tt because doing high avg mu areas gives a drop in tt returns from what i have noticed. If you want ur tt back up, you might want to change that.
2. For me i was break even or close despite the low tt returns which am guessing is true for you as well, you might want to disclose that.
Bottomline, you cannot just keep focussing on markup and expect tt to come back someday. In my personal experience, it does not work that way. Need to balance the tt and markup at some point. In my case downgrading to a lower amp+doing more mu balanced zones also helped quite a bit.
It also makes sense overall because unlike hunting, in mining you can very specifically target the markup and go for those based on depth/timing etc. The system is built so you cannot blindly just focus only markup and keep profiting without any regards to anything else.
Personally, I think it is a very balanced system.
Divinity
PS: The only place where i have seen markup and tt consistent is lootable pvp :-D