I assume that the section of the USDA article you're referring to is this:
Partial Cooking
Never brown or partially cook beef to refrigerate and finish cooking later because any bacteria present wouldn't have been destroyed. It is safe to partially pre-cook or microwave beef immediately before transferring it to the hot grill to finish cooking.
Before I go on, I should point out that the USDA obviously has much greater expertise than I do when it comes to food safety. Nevertheless, I find this recommendation to be extremely bizarre bordering on silly.
For full cuts of beef (not ground beef), bacteria should only be present on the surface. That is why most people - or at least most people I know - choose to eat their steaks rare, or at most medium rare. The "interior" is not fully cooked, nor is it supposed to be.
Searing the beef will kill any surface bacteria almost immediately. That is why rare steak is (relatively) safe to eat. As far as I am concerned, once the beef has been browned, it is already cooked sufficiently. The only reason to add it to a slow cooker later would be to tenderize it or even out the cooking.
If the USDA expresses concern over refrigerating beef that has basically been cooked sufficiently, it must be because they believe that browning/searing kills enough of the bacteria to make it safe for direct consumption, but not all of the bacteria - such that they could multiply again and contaminate the food over a long period of time.
But refrigerating immediately after browning should prevent that. No part of the beef will be in the "danger zone" for longer than 45 minutes or so, and even if you did miss some of the bacteria during the browning and they manage to multiply overnight, you're still tossing them into a slow cooker and that's going to kill any remaining bacteria.
Perhaps I'm missing something obvious, but from what I can tell, any health risks associated with browning a large cut of beef and subsequently refrigerating it for a relatively small period of time would have to be infinitesimally small. It's not something that I would concern myself with.
Edit:
I did just think of one other possible reason for the USDA warning. The key phrase is "partially cook." If the browning is being done as a means for shortening the subsequent cooking time (i.e. slow cooking for 6 hours instead of 12), then you might have a problem. Because if you don't manage to kill all the bacteria, then the total required subsequent cooking time is going to creep back up as they multiply; that means your 6 hours in the slow cooker that might have been enough if you had seared the beef immediately before, are no longer enough to guarantee safe consumption.
So I am adding a caveat to my original answer: It is probably safe to refrigerate the browned beef, but you should calculate your cooking time as though you had never browned it. If you are concerned about safety (and I maintain the risks are minuscule), then treat the browned/refrigerated beef as uncooked meat. If you do that, I cannot see any reason why this wouldn't be safe.
There is no rule, you should use the cooking times in your chart or a reputable timing chart, I use this one hippressurecooking.com/pressure-cooking-times
Basically, you'll want to phase-in the ingredients. That means, cook the beef roast for the time your cooking chart says, say 30 minutes, then open the pressure cooker and add the vegetables and pressure cooker them for their cooking time 4 minutes.
BTW, that same blog has a section where you can post a recipe and they will convert it to the pressure cooker for you. That's here: hippressurecooking.com/recipe-conversions
Best Answer
As logophobe suggested in the comments, look for slow cooker recipes that aren't soups or stews. There are plenty, mostly in the direction of roasts. The general idea will be that you put a large piece of meat (and maybe some vegetables) in a slow cooker, with a very small amount of water (maybe half a cup), and you'll end up with some liquid in the bottom, but not a huge amount.
That liquid will generally be pretty flavorful, so most people would probably eat it somehow. One might eat it with the meat, turn it into a gravy, or use it in a different soup or stew. You should be able to make something pretty delicious; I wouldn't think of it as "watered down". But if you don't like liquid, you can throw it away.
If you don't like any of those ideas but it still seems wasteful (it is), I guess you might want to pick a different way to cook meat. Slow cookers are pretty much capable of stewing and braising, which can give you something pretty much like a roast, but there's always going to be at least a bit of liquid involved. If that's really not an option for you, the slow cooker might not be the best choice for you.