In my opinion, the big version of golems, wolfs and ents appear to soon in the hard mode. Especially the stone golem is nearly unkillable with all his armor.
In my current playthrough, I’m at day 8 and was lucky enough to trade 3 iron pikes. 2 of my 8 hearthlings are footmen and both managed to be lvl 3 already. So you can say I had a really good start. But then a big stone golem came. Even with my 2 iron pikes, I dealt close to zero damage to him. He on the other side managed to do 1/8 health damage to my footmen with each hit. In the end, the stone golem had a little bit less then half his health, while both my footmen died. I tried to distrubute the damage between both footmen with micromanagement, so that they were alive as long as possible during the whole fight. But I really had no way to kill this game. In the end I had to reload and use a different tactic. While the golem followed my 2 footmen, i let my hearthling build a ladder to a lower plattform. Then I lured the golem to this lower plattform (luckily those guys can climb ladders, lol). When he was far enough away from the ladder, I got my footmen to the upper plattform and let my hearthlings remove the ladder. After more then a half day, the golem finaly disappeared.
All in all I suggest that the big golem does not appear before day 15. This is enough time to prepare at least 3 fighting units and maybe a knight who can sustain the damage. The other big version shouldn’t appear before day 12. They are also heavy, but at least killable for footmen.
I also found a problem with the new AI from the military units. When you bring your hearthling into a safe zone (example: in a tunnel with dunnel door) and you also want to bring your soldiers to the safe zone, you must place a defend area in the tunnel, otherwise your soldiers will always go for the enemy. But when your soldiers get tired, they just run out of the safe zone, no matter if a stone golem is waiting for them. They even try to sleep while being next to a stone golem… lol. The only solution for me was to place the beds inside the tunnel. But still, they shouldn’t try to sleep when an enemy is close to them.