Mod deleted my previous post because I swore too much due to the auto-tagging system the forums use making me lose multiple paragraphs of response due to too much formatting, and the formatting came from the CH formatting of my original post being edited and nothing to do with what I was adding.
Anywho, bots will not pick up grimoires unless a mod like IAmLupo's comes around that changes the behavior via lua scripting (this trainer will not be able to solve this as it edits memory and not scripting, otherwise we'd have way more options by now).
The reason they will not pick up grims is because if you've noticed, they pick up everything. They've even found tomes I was unaware of that were nearby for me in the past. Now look into the eye of someone playing legit on Champion. The top tier (and sometimes the one below) difficulties and those that play in them always make the choice about how many grims to pick up (based on the experience and ability of the group). If picking up both grims is a guaranteed one-shot (which is usually the case on the highest difficulty), you do not want bots picking these up and making the difficulty that much harder. Not to mention they can no longer hold pots for those that need them if this is the case.
What would be nice though is if the trainer added a the option to give the player 3 tomes, 2 grims, and 3 loot die from the start of the match, which is very possible via memory editing, to guarantee a decent chest at the end.
The best farming level without a doubt. Personally I'd Waystalker over Shade due to being able to spam trueshoot and kill basically everything you see as (and sometimes don't see) while maintaining stride, but I personally always go handmaiden for the speed. This level is great because the tomes and grim are almost all on the way through the level and like you said can be finished incredibly fast (my quickest is around 6:40 by using the console trick to move during camera cutscene so i can spam handmaidens ult and clip through the wheelbarrow so by the time the overview cam finishes you are at the first barn. I personally get all three tomes in case I get a die which usually knocks up the chest to the next level.
Also there are ways to manipulate where the bots teleport to (spamming handmaidens ult makes them teleport like crazy), so the two areas with guaranteed health (the area before the ladder leading to the locked barn and at the windmill with the general bridge). I generally get to the straightaway to the ladder, let the bots get around me, and get halfway to the ladder, then spam ult and as soon as i'm up the ladder spam ult until I'm at the grimoire barn, which will teleport the bots from before the health pots to said barn.
As far as the windmill bridge with the general inside and second guaranteed health spot i dont use the ult after getting up the hill so the bots stay busy spamming their abilities on the mobs it's easy enough to get past that L turn in two ult moves, then spam until you are at the first locked cage and forcing the bots to teleport from just before the health pickups to the locked cage.
After that, bob's your uncle as they say as there will likely be no more health items on the way through the level close enough for a bot to get, especially if spamming handmaiden ult, unless you check the chest in the final barn, it spawns a pot (hasn't happened for me ever but it's RNG unless that chest just -can't- spawn health items), however I ult to that room from the part where you jump down so the bots dont make it into that room by the time you're up the ladder and at the bottom two cages.
Everyone has "their" their method though, and that's just mine. Maaruk's advice is definitely adviseable and I can't think of a better level than against the grain to farm for either xp or chests. Best thing you can do is experiment. You'll find tactics that just plan suck and may take you 30 minutes to finish a level (or more if you want to power level a character you haven't started yet on champion because any special that spawns will take awhile to kill unless you get lucky with a bomb and can use infinite ammo (which I only ever use if no bot has picked up a healing item so they don't get infinite ones), then specials go down after like 10 bombs or so (dunno, never counted, just know it drops bosses and specials pretty fast). Point being experiment, learn from mistakes, learn what works, and learn how to save time first and foremost. If you don't bother with chests, one/two tomes and one grim can give you the same chest as three tomes and a grim depending on the blessing boost.