I just spent a weekend teaching an AOW class where I required the divers to maintain eye contact on all ascents and descents. What that involves first of all is good communication between the divers. Not just up and down but before they even get in the water. Next it involves proper weighting. OW divers should not need a DM or Instructor to check their weights or tell them how to check their weights once they have that card in their hands. The buddy teams should be checking and verifying each others weights before they get in the water. If you are buddied up with an instabuddy somewhere you should ask them how much weight they are carrying, how it is distributed, how do you release it, and how did they determine they needed that much. IF they don't know - I would not dive with them.
Next when you do your final check before stepping off the boat, unless it's a hot drop (which a new diver should not be doing anyway), make sure your buddy puts some air their BC. Then drop and descend together. Eye contact and touch if needed to stay within arms reach. My rule is the slowest diver sets the pace of every phase of the dive. Descents, swims, ascents. Screw the DM, Guide, and everybody else. If one diver has trouble equalizing their buddy does not drop to 30 feet and wait for them to get down.
That kind of stuff will occur when doing hot drops, tech dives, and when surface conditions are such that staying on the surface is not as safe as descending 10 or 15 feet. But then you still need to ask how much do I care about my buddy, what will I do if the panic, or what will they do if I have a problem and need them. Sometimes its better to not do the dive if you have to think of those things because of conditions.
Your buddy is your buddy or they are not. You are theirs or you are not. There is no middle ground from my perspective. I am either someone's dive buddy or I am alone.