1-40 meleeing is more mana efficient than root rotting, especially on Blue when you have access to cheap, good ratio weapons like:
https://wiki.project1999.com/Poison_Wind_Censer
https://wiki.project1999.com/Granite_Face_Grinder
https://wiki.project1999.com/Exquisi...um_Brawl_Stick
Shaman DoTs have bad DPM at lower levels, and spell resists hurt a lot mana wise.
With meleeing, you just need to haste yourself, heal yourself, slow, maybe malo, and only root at the end when the mob is running. You reduce how many spells you need to cast, and you reduce how many spell resists you get. This is because you are healing yourself, instead of attacking the mob with DoTs. You are also not rooting as much. Lower level roots have a smaller duration, and random root breaks occur. Mobs don't do a ton of damage levels 1-40, so the damage you take while slow tanking is pretty efficient.
Once you hit level 40, meleeing becomes a lot less efficient. Mobs hit a LOT harder, have more HP, and more AC. You also get access JBB and Epic in 5-6 levels.
Shamans were designed to melee to a certain degree. This is evident by their 200 maximum skill for weapon skills at level 50. This is the same cap as Shadowknights and Paladins. Druids and Clerics have a 175 cap at level 50. Also, Shamans get a specific buff line to help with their meleeing:
https://wiki.project1999.com/Frenzy to
https://wiki.project1999.com/Voice_of_the_Berserker . Not saying it is an amazing spell line, but the game design is crystal clear.