Well, the thing is, it's really not much difference than sc ... only difference is you must play much more carefully. Because bowa needs good gear in order to make progress in hell mode, both in sc and hc.
But .. you CAN make progress with mid-range gear too. Only thing is you need at least a semi-strong merc, and lvl 20+valkyrie, and utilize them to the fullest. Make them go upfront always, don't rush ahead. Always cast decoy in front at least, and let them engage while you stay at support range.
I personally like strafe better than multishot. It gives better control of the situation.
Any exceptional unique bow, or especially the harmony runeword in a decent bow, can make progress in hell mode. Witchwild string is a one-off. When the amplify damage casts, the monsters do go down quite easily. That is why i like strafe, also atma's scarab is perhaps the best item for bowa in this sense.
You will always struggle with hit points as a bowa, unless high end geared. Around 1000 hit points is normal, and maxing resists is always an issue. So you simply cannot tank much. But, when or if you get used to playing defensively, you can absolutely make progress through hell. Only real big hazards are ranged boss monster packs, and if lacking resists, watch out for the cold/lightning enchanted boss monsters.
As written, at least a semi-strong merc is in my opinion, necessary to make it through hell. Insight in a good polearm, something like a good treachery or duriel's shell, and some kind of leech helmet (blood crafted helmet is an option), is a bare minimum.
But yes ... moving on to hell mode underprepared is going to result in two things: A quick death, or extreme frustration and hard work of barely making any progress. And empty pockets after merc repeatedly gets slapped into oblivion by the first zombie boss pack you meet.