Gold is harder then say Blue. Most folks just stick to Blue. It's easy(Face roll easy). Least on my server, most players rather sit on a farm or 50 group and get PL'd. Having someone else play the game for them.
From easy to harder for it's level range: Blue, Red, Gold. (Though red can spike over gold with stuff like say Goldbrickers & Longbow).
Gotta realize, your facing stuff that you normally wouldn't see at specific levels. Lvl 1 alone, your already facing Energy & Psionic attacks. With lots of Mez & AOE. So you decide we'll I'll team up. That just means more of that.
Well, lets make optimal team. Say 4 man team of a Tank, Mastermind, Controller, & a Corrupter.
Doesn't matter what you bring, at those levels, it's going be hard. From Explosions, CC, Dmg types you don't normally face at lower levels on Blue. (Though Red is very well aware of that). The mobs AI is a bit better in it's cycling of attacks. They'll actually run away and try bring friends back, etc..
Ghouls...man...Pack Tactics is their foray. If your not paying attention and just smacking away, not understand why stuff not dropping or as fast as you like. Probably a Painted One hiding in there healing & Buffing.
Many mobs make use of Leadership buffs inherent. Even if you have decked out 50s, Mal' downed with n00b leader, forking out missions. It's still going have rough patches.