It must be a nightmare for all you 60 Omni-crafters
I have all but one crafter and one gatherer at 60 - my only gripe (from a crafting perspective) is lack of space across the board. I am a walking storage (only 1-4 of my personal inventory tabs are free [by choice] so I can loot during gameplay) - every other slot on me and my 2xretainers are chock-full of crafting & gathered materials. Why do I carry so much with me? Because I craft often, and I absolutely detest having to play the 'call 2x retainers multiple times while trying to collect your needed materials [to make more materials] game. It would seem someone like me would do well to rent a third retainer, but that remedies a gripe by extending a different one (more space but even more farting about when looking for materials spread across multiple storages). I'd rather make do with what I have. Item stacks are of very little concern to people who can consistently craft HQ versions of practically every non-master recipe in their sleep. You'd only really stock up on them for levelling purposes (and even then, you wouldn't need to stockpile tonnes of them), or if going for particularly difficult recipes and want to squeeze in every single HQ% possible (regardless of level).

I'd be perfectly happy if, say, when within a certain radius of a summoning bell, you can craft as if both your retainers and your own inventories are as one (eg. like TESO - if you're in town, anything in storage can be used as if you're carrying it personally - the flavour text being that said materials get carried to you on demand). The way it currently is is perfectly do-able, just extremely frustrating if your storage is being gobbled up.

Might just be me.