In terms of a serious threat in blue that costs five mana Meluko trumps all the alternatives however when facing the likes of Banelsayer Angel, Wolfir Silverheart, Seige-Gang and Thundermaw Hellkite from other colours you are much better off casting a Time Warp and making a six drop
At that point, you can kill them with three Simian Spirit Guides and a Conflagrate (one to cast it for zero, two to flash it back) or three Spirit Guides, Seething Song, Through the Breach, and Emrakul
Zur, Eternal Schemer Adding creature stats to your enchantments makes your board way scarier, and Zur, Eternal Schemer does exactly that
It's a fine card for what it is and does
Ryan C's primer is an extremely handy guide to this deck, if you want a fuller understanding