[2019] Yeesh Dark Zones beat the crap out of me, not just on hard but challenging. Help?

World Tier 1, Gear score 320, skill power 1200 or something. Been playing since game came out and just now decided to try the Dark Zones. I am not a Einstein when it comes to all the builds and stuff but have caught on and have modified every piece of equipment, really juiced up turret and drone atleast compared to early in game. Is it just to early to take down these landmarks I am always in cover and noticed enemies are tougher everywhere in game since before endgame but I get hit with grenades, bosses are now bullet sponges where as before my LMG would rip them apart. Do I just need to level up more or what am I doing wrong. Also can I use a backup to help? Thank you and enjoy your day.