I suggest you go
here and fill out a Configuration, so we can accurately see what you need to fix up
It's a very useful tool, here are a couple of mine.
http://auno.org/ao/equip.php?saveid=35987
My Doctor - Stillian
http://auno.org/ao/equip.php?saveid=42896
My Engineer on Test Server
http://auno.org/ao/equip.php?saveid=43691
My Agent
So, with this tool, we can quite easily help you along, a lot!
Heckler's are (I only know Omni Garden exits, sorry) at 'The Core' and at 'Brawl', and are indeed in the Shadowlands.
For a free player (or for any player of your level) I would suggest:
Teaming in Foremans.
Team missions.
Cyborgs in Mort.
I personally like missions, because they give loot, experience, credits, and the all important tokens. Yes! Work on your token board whenever you can. I seriously regret ignoring that with Stillian.
For Agents, look into the:
Grip-Com (not sure of the spelling here) series of weapons.
The Yatamuchty X-3 Counter Sniper Rifle
The Caterwaul
All 3 are reasonable weapons, and I say (offhand, since my Agent is a bit of a bread and butter one - Perennium Sniper since Level 20) that the X-3 might be a good choice for you. It has a reliable Aimed Shot and good damage.