Hardcore conversation? have no fear.. disco is here..
problems you need to address when making a build for HC, I've HC botted to over 1.2k paragon, before the crazy grifts, so when 40 was max I was over 1k, I haven't botted that much HC lately because I've lost interest in the random blizzard lag spikes that can rek any build. With that in mind
1) before you are pushing, you need to have backup gear, at least 1 item of each to make ur character back to regular botting, and on top of that gems leveled. (absolute must) now with the gems into items, this might be a while, because you'll need ur 3 regular gems plus ur 13 gems into ur items.
2) don't be cheap with the gems into ur items, you might want to get them an extra 5 levels higher or wait a bit longer. Not worth it, get them into ur gear as soon as possible to increase ur ability to clear/survive
3) keep in mind ur toughness and how it's works, by this I mean, one of the above posters mentioned that he has a barb and ancients. This is all fine, but DB is unpredictable, so having 1 billion toughness when ur hero is active, i.e WWing, using a generator is close to useless. I've watched characters that have died because the navigation server hasn't sent them a signal, so they start a grift (x) and they are just standing there, or walking around without doing anything. Then an elite pack runs up and almost 1 shots your hero, or does so. I've jumped in and used the door to keep my bot alive, but he has died plenty of times to that. Back to my original remark, you need to make a hero that when standing still doing nothing can survive, the LoH crusader is good because he has great survivability without any active skills required
4) the hero has to survive through harry situations, by that I mean, ur fighting 2/3 packs, DB crashes. Regardless what toughness you have, without an adequate amount of DPS to clear that before it clears you, you will die. When DB d/c's you are stuck in the game in that exact spot until the diablo 3 server kicks you. I'm sure it's upwards of 20 minutes before that occurs so u need toughness and inspect ur hero when he's running grifts. Check to see how he does when u have 2/3 elites around u, play urself by hand and see if he can clear them. Do lots of testing in very annoying spots ur self to understand what will get u killed fast. Push as high as you can manually so you're able to get high gems on ur character, if the bot can do 50, you can do 70, that's a 20 level difference between the gems, that difference will make or break ur character when DB crashes or fucks off on you.
5) make a sc account, get a character or a couple up to 70, preferably characters that you're hardcore botting with, gear them in a similar way that ur HC account is geared. Then when there's a new DB update to Trinity/Adven/DB/whateverelse you use, run that account first for some time. The programmers do an excellent job at getting the system running well, but sometimes an unexpected bug arises and it causes ur character to not function ideally. By doing this you can run ur bot for a couple hours at least and get an idea if everything is okay, when you check on ur bots progress and u notice that it hasn't died in x hours, then you can log onto ur HC character.
6) never make big changes without watching ur bot, something as simple as recasting ancients for a barb isn't an issue. Unless db doesn't cast ancients until they are ALL dead, so now ur hero is running around with 2 ancients, then with 1 ancient, then u get jumped by a pack of elites and pop goes ur hero because they froze it and u couldn't recast them for the extra toughness.
7) don't assume, "the law of large numbers A principle of probability and statistics which states that as a sample size grows, its mean will get closer and closer to the average of the whole population." you're not creating ur bot for this, ur bot is made for the 4 elite packs or 3 + guardian, the average rift is something that should be a np, you make ur character for the random stuff that it needs to live through
short note, you could also try WD pet build, lots of toughness and the pets do damage, but it does nothing for u if u've entered a grift and the bot doesn't auto cast all ur pets
8) avoid barbs, monks, DH, wizards if you plan on farming 58+, they are too reliant on generators to sustain toughness, the grifts past 58 have some sort of significant dps increase in them (personal observations, no data behind the last statement)