Base Damage: 29-35 (Low)
Damage Per Weapon Improvement: +6-9 (Below Average)
Attack Speed: Above Average
Attack Range: 600
 Skill Build
1 Mass Regen
You want to pick up Expunge early for the snare. There is no dire need to have the regen/totem skills maxed as early as possible, unlike most heroes skills.
 General Strategy
As you can see, Shaman is all about utility and versatility. His healing is very strong and his two snares can help kill enemy heroes. However, he is lacking in offensive capability.
You can either do a spawn suport or an attack damage based build.
An attack damage build takes advantage of your multi-hit, and reasonably fast base attack speed.
A spawn support build focuses on you mantaining mana to help other heros and your own spawns
Early Game - Your Regen will help you push and negate any nukes that may fly your way, and keep you from needing any healing potions except maybe 1 or 2 for emergency. Look for good opportunities to Expunge any enemy melee heroes that linger too long on the front lines. Your troops and long range attack will punish them for their insolence. Try to save 200 mana for your mana recovery combo at level 15.
Mid Game - Your attack will still be pretty weak, but if no heroes are around you can run behind the tanks and drop a fire nova totem to wipe out mage/archers. Use your ranged attack to bounce around mages/archers if possible without taking excessive damage from enemy ranged heroes. Remember that you can heal and your attacks will bounce unlike theirs. Healing is very important.
Another interesting strategy to do here around level 15 is to start buying critter-creation items from the Goblin shop, and use them to assist with pushing and farming gold. The first available is the Sea Elemental which has 800HP and a decent ranged attack and is very cheap for only 85 gold per critter. After a while, the mighty Sludges become available which has double the HPs and attack capability plus the ability to split into smaller versions when it dies. The concept is that the Shaman can use his AoE heal to keep his critters alive, and thus get a lot more use out of them as opposed to most other heroes that cannot heal non-heroes. (Oracle and Blazing Priest can sort-of use this strategy too)
This is a pretty effective strategy during the midgame as it is extremely difficult to kill a 1600HP player-controlled ranged creep that can heal at 40HP/s with Mass Regen on it. Enemy AoE spells are easily negated with Mass Regen. Each critter can bring quite a bit of firepower to bear for their minimal price tag, thus being much better than using mercenaries or other gold spending sources. As the game progresses, the Shaman can continue to build up an ever increasing horde which pushes and farms very effectively.
The only downside is that it requires a lot more micromanagement skill to implement. However, the shaman is not particularly difficult to use for the most part when pushing so this is not a huge issue. After all, the Shaman tends to spam Mass Regen and autoattack.
Late Game - With a few items, your autoattack is pretty strong. You can wipe out small clusters of troops with fire nova. Your heal is maxed out and lasts for a long time. Use it on your troops whenever possible.
 Items and Enhancements
DO NOT get the Orb of Fury!!! It will mess up your attack, such that you are firing blanks from then on! Literally... you will toss absolutely nothing 100% of the time and do no damage.
Do NOT get the Gloves of Crit either. When a crit occurs, it disables your multiattack. This is ok sometimes, but overall it actually decreases your damage.
Once your orb is maxed, there are several other items you can pick up which are less efficient but useful. In no particular order, these are:
- Sun Talisman - You don't need the HP-regen so much, but the other properties are great: More HPs, attack speed, movespeed, manapool.
- Dragon Heart - I would not pump this item up until last, but even at base level, the attack damage is beneficial, and the mana regen boost is extremely strong since you cannot really spare an orb or helm slot for a dedicated mana-regen item. 60% mana boost is a LOT. Plus, the dragon summon really helps your weaker early offense.
- Helm of the Executioner - Heavy attack damage makes this a winner, although it is about 40% less efficient than the orb of battle for this purpose.
- Zephyr Thing - This is an excellent item, as the attack speed is great to have. Blink is incredibly useful for the Shaman for escape or hero pursuit. Blink + earthbind is massive ownage vs fleeing heroes. Remember, your offense is limited to your autoattack, and this is the best way to actually get kills. Don't upgrade until very late, as it is too expensive just for a quicker cooldown and faster attack.
- AGI gloves - Not as useful as crit gloves should be, but its still a solid choice. Helps with hero pursuit, adds a bit of damage, and gives a big attack speed boost.
- Leather Armor - An efficient item with lots of useful abilities. The attack speed is welcome, as is the armor and evasion.
Note: If against a hero lineup that can inflict massive damage in a short period, you may need the sun talisman or another HP buffing item for survival. You can heal most damage, but that doesnt matter if you get 1-shotted by the Infiltrator...