If you want some tech, I like to run a few Deadly Shots to take care of turn 3 giants, and it's pretty good against druid for turn 4 Archmage Vargoth as well. The issue against Druid is that you have no good way of dealing with a wide board, so you have to slowly clear the wisps while developing a massive board through Oblivitron and Mechanical Whelp. Against Khadgar Mage, you have to apply pressure constantly. You know they don't have Polymorph, so go ham with your magnetics. If you keep putting pressure, you will be in a spot where your opponent can't just play Giant without tanking a load of damage. If they do get their combo off, it's near impossible for your deck to come back unless you just have lethal.