OK, here's the dealio.
You are playing BNet, so ATMA/GoMule does you no good - those are for SP characters. It does sound like you've been going solo, though, so I think you will get a lot more satisfaction doing this without help from another character.
This also means boss running will be much more difficult for you since BNet games reroll maps every game - the exception here is, of course, Pindle (assuming you didn't activate the Halls WP and kill Nilly, which, being a n00b, you probably did).
You are trying to make your Drood a Slayer, so NM Countess running is not an option for this particular pickle.
You have been doing the typical n00b mistakes (I did them too, pursuing max defense and all), so your gear/merc/etc. selections need to be rectified.
So, based on what you've read, you've gotten an A2 Off Merc (Blessed Aim), and need a good weapon for him and your drood.
First, some questions:
Have you been collecting runes, and, if so, which ones do you have right now?
What items do you currently have at your disposal?
Do you have a mule character? That's a character you don't play, but just use the inventory space to keep stuff you aren't currently using.
Now some answers:
Runewords are specific runes set in a specific order in a socketed normal or superior item (NOT magic or rare) that give it unique-style mods.
The runeword weapon I advocate for your merc is 'Strength' (Amn Tir) in a 2os spear or polearm. I suggest this because 2os items can be found in Normal, and the crushing blow it gives you is independent of damage dealt and it provides something I bet you didn't know is essential for a merc - life leech - that means he gets healed a certain percentage of the damage he does to monster. Find a 2os Poleaxe, Spear, Lochaber Axe, etc, and if you have an Amn rune (Tir is trivial), you can make this for a weapon that should serve your merc until you find something better.
The mods you want for your merc are Faster Hit Recovery (FHR), damage reduced by X, life leech, resists. Defense is helpful, but certainly not top of the list in importance. A rare armor with some resists and FHR would be fine until you find a really nice unique armor for him.
The best helms are definitely the uniques - there aren't a lot of runewords for them, and the set helms are spotty. A VERY good choice for you or your merc that is easy to find is Duskdeep - another good one is the Face of Horror. Lore (you need a Sol rune and an Ort rune) is a handy early runeword (I suggest that for your drood), and if you find a handy 2os Druid pelt with some nice staffmods (+skills to certain druid skills on a normal item), it's certainly not a bad choice.
Weapons/shield for your main character... Well, I agree that Rhyme in a 2os Bone Shield is a super choice for early to mid game, but it requires a Shael - if you have on, definitely shop that Bone Shield or use a Grim Shield. For a weapon... well, anything giving +Druid or Elemental skills since you are playing an elemental druid. For some good damage for melee, I'd perhaps suggest 'King's Grace' in a War Scepter.
Gloves and Boots - I agree with the vote for gambling rares - these can provide some nice mods (resists, Increased Attack Speed, FHR, Faster Run/Walk) and rares can trump set/uniques in these categories.
My final piece of advice - this requires a big sacrifice, to be honest - is to start fresh with an SP character - this allows you to use ATMA or GoMule to have an easy, infinite stash for items and keeps your maps the same so you can easily run bosses for items. Other perks are NO LAG, Save & Exit screen pauses the game, and the advice you get form folks here will be applicable to your game.
