Why on earth would you want to manor on yellow to red mobs?
For 20-40 you want a palus knight or, if you're willing to guzzle pots, an assassin or rogue.
For 40 or above, there is one and only one choice - and that is the summoner. Nobody else manors nearly as well - of course, they don't have ANY effective manoring ability 10-40.
the use of yellow to red would be for higher returns on seeds, for example, when i killed a pink x4 hp mob, i got 7 seeds, but killing x4 white mobs gets me 5, and green x4 gets 4 seeds. that's why.
Actually not always. I was around level 30, farming in NoS, using seeds 11-21 on green/light blue mobs. I harvested 12 seeds usually, 14 max. I really doubt I would get more, being aroud or lower level than seeds.
Harvesting success depends on you being near the mob's level - if it's too high or too low, you'll fail the harvest.
Sowing success depends on the level of the seed in comparison to the mob, and it might increase a bit if you're higher level than the mob (not 100% sure).
In either case, the quantity of crop returned depends entirely on the mob and the seed.
To add in my two cents based on my own observations.
Sowing: Seems to work a bit like 'Grade Masteries'. That is, if the seed is over your level you have a penalty to sow. Also, there is a penalty to sow anything below Green mobs. This part of the penalty is tied to *your* level and not the seed level. Finally, yes there is a penalty to sowing mobs above the seeds level. This is the smallest penalty, and you can usually sow up to 10 levels over and still get a good return. The sow bonus is almost always greater than the sow penalty in these cases. (Some seeds almost appear to be *designed* to be used above their designated level in fact.) The bonus for sowing on xHP mobs is well known, although previous testing has strongly suggested that this is due to the XP of the mobs and not their HP.
Most of my testing has been done on mobs I can solo easily, thus I personally cannot attest to the effects on sowing yellow or higher mobs.
Harvesting: Once sown and the mob is killed, harvesting appears to be solely affected by your level in relation to mob level. Thus mobs that are lower than green have a increasing penalty to harvest regardless of any other levels involved.
sowing: chance of success based on seed level in relation to mob level. best returns, as a general rule, are on the upper end of that level, 5-8 levels above the seeds level. in addition, certain mobs, even though they are x(whatever) mobs, will give you uncommonly high return rates for certain fruits. example, 14-15 great codrans from angels on TOI 9, per seed.
harvesting: chance of successful harvest reduces by 5% for each level "into the blue" the mob is. seems greater if you go above white mobes, maybe its -10% success each level of "into the pink", but no proof of that.
I almost always used seeds on mobs of the same lvl range than me. ie. if a seed is lvl25, I was between 20 and 30, and the mob too. And on some 1x HP mob it often failed. But... I don't remember which mobs (maybe some lizards near Gludio) nor if it was sowing or harvesting.
On a side note, I think every non-ranged class can be good at manoring. Including scav, they can spoil and sowe the same mob, making them work twice more efficiently :)