I'm back after running a few solo leves with the goal of finishing them in under 5 mins for max SP. Did 3 runs as a 24 THM at Camp Drybone (just to get some numbers) - Results:
5 star - 24 THM solo - Avg SP/Kill (NO GF): 45 - Bonus SP for completing under 5 mins: 138
So with an average of 7 mobs per leve ("The Enemy Appears"), being 14 levels over but finishing a 5 star in under 5 minutes nets you 453~ SP.
Ok! Let's move on to Camp Horizon with our 24 THM and see what the SP is like..
The Devilet Inside - 1 Star - 24 THM solo - Avg SP/Kill (WITH GF): 61 - Bonus SP for completing under 5 mins: 960
A Leg Up - 2 Star - 24 THM solo - Avg SP/Kill (WITH GF): 72 - Bonus SP: 840
So.. 1500~2000 SP for 5 minutes work doesn't sound like such a terrible thing.. until you factor in you can only do so many leves at the optimal rank, with a cap of 8 per 36h.
I can take my 24 THM to Nanawa Mines and try there.. but then we're not really talking "casual" play at that level.. It's possible, sure. Probably not for the average weekend warrior though.
So to sum up: Don't use GF, or bother with leves at all until level 30..? I'm not sure how else to take the results, but yeah this is a ridiculously small sample size. Can someone else post pre-30 solo leve results? Either way, I'm pretty certain it won't stay like this too long. I'm completely underwhelmed, unless I'm still doing it wrong. I welcome feedback
