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Rune for home + commodity deed box = a pretty quick drop off and return system (just as much as a bank).
Only exception would be if you were going further and further down into the bowels of Ilshenar dungeons, but then if you're just looking to farm certain areas for whatever reason, even in Ilshenar there are places to make the need for a Bag of Sending non-existant (due to gypsy bank and moongate placements).
Seeds could have helped PvM quite a bit, but they drop too fast. Just a few kills and you're set up for a given group, an hour or so cycling through the groups should give you all you want from each batch if you're going for a set (or if you're going after one particular plant, staying with one creature will give you enough chance to get that plant).
What PvM needs ISN'T the return of the bag of sending for heavy items, but more uncommon and rare drops that are used in other places in the game (the spring cleaning items that were active drops were reasonable examples).
One good example of monster loot is the ant lion. A decent amount of gold, and then a batch of items that are useful in other areas (fertile drit for plants, ore for metals, junk magic items for recycling, skeletal pieces for bones, new seeds, and the occasional "skeleton of a random type" with a little bit of extra loot).
If you try to grab everything, sure you'll be full in a heartbeat, or if you focus on specific items (i.e. dirt and seeds only, or bones only, or bring a fire beetle to smelt ore), you can stay down there longer.
Still I'd like to see special uncommon/rare items drop that are used for other purposes be it crafting, new quests, or whatever. The question though is what should the drops be and at what rate should they occur.
Right now a LOT of monster loot is waste because it either drops too fast, or the system involved has become overly stale (such as treasure maps).
I'd say that the problem with PvM is NOT the Bag of Sending nerf, but the general lack of excitement in monster loot as a whole. Instead of hoping for a special drop, and feeling accomplished when it happens, PvM has been a "farm as much in resources as you can" activity which is why teh Bag of Sending nerf had such an impact.