I've played medic both before and after the crossbow meta. Crossbow is overpowered and breaks the mechanics.
Anyone who is saying it should be nerfed; its not going to be nerfed. Valve doesnt care. The only solution we have as a community is banning.
The weapon takes little skill and trivializes a lot of skillsets. Examples on top of my head:
Managing your and your teams damage - your entire team gets a free jail card from red health to full in a couple seconds. Pushing on damage is obsolete and playing aggressively is punished.
Managing you and your teams positioning relevant to the medic - get an arrow from 30 meters away = never have to leave/manage health and kits on flank.
Spamming chokepoints or fights with arrows isnt skillful, standing still for arrows isnt skillful, hiding behind cover to get arrowed when you would have died without crossbow isnt skillful.
Before arrows existed you had to heal with mediguns, which in my opinion is a true test of your skill and game sense. Your positioning relevant to the map and your target, potential threats, healing priority, and damage/health awareness. No crutches or gimmicks. Arrows essentially circumvents this by granting you almost infinite get out of jail cards, say the medic spam-healing his team for three times the efficiency. In practice, arrows break the health mechanics when properly used.
I think the solution is to ban the weapon since Valve is out of touch with the competitive community. Although it is unlikely for the weapon to balanced, here is how it could be balanced:
Arrows can continue to serve their purpose of healing outside the medic's normal close-range heal with the medigun, but at a reduced rate to combat spamming arrows, and a penalty for for using arrows close to your allies. Instead of being a 75~ hp burst at close range, it needs to be lower, something like 25. Having the weapon do minimal healing up close would prevent breaking the healing economy like explained above, and also greatly reduce healing over range. Something like 25(close)-50(long range) would be much more balanced than 75(close)-150(long range) and no passive reloading.
Making it a flat number of 25/30/35 would prevent outputting massive amounts of healing just because someone is far away, but still be able to save people from fall damage or give them a bit of aid when they're out of reach. Spamming choke points or players who are in combat isn't skillful or has anything to do with risk/reward, its more no risk/reward/reward.
Lowering the healing number by this much might seem like a drastic change at first, but if you understand the health economy and how burst healing destroys a large part of the game (health management, heal priority, pushing off damage etc) it -needs- to be heavily nerfed, while still maintaining some utility at range. In its current state, the utility is way too powerful at range and too powerful up close.