Hearthpwn

I have the same with a dragon package, works very well too!

Where does Shotbot come from? it says I'm not able tot craft him

It comes from the Galakrond's Awakening solo adventure.

 http://www.hearthpwn.com/decks/1337367-pure-libram-paladin

 I understund that's deck id aggro/tempo?

Why no Murgur? Even by itself without any support for murlocs, it's a strong card. A 2 mana 2/1 with divine shield is decent without taking into consideration the Prime effect. Since this is a deck that aims to close out games later rather than sooner, you will be able to draw the prime in most of your games and play it as a secondary win condition. Summoning four random murlocs with divine shield can win you games by itself, and there really isn't a reason not to run it. It's a lot better than quite a few cards you included - taking out both imprisoned sungills or righteous causes would get rid of cards that will very rarely be useful to you and allow you to sub in Murgur and a second Libram of Hope, another card that is bafflingly missing from your deck.

I wonder if is it worth to drop the whole ''pure'' package, to spice things up with Kael'thas Sunstrider and Archmage Vargoth.

The Libram of Wisdoms are going to cost 0 pretty quickly, so besides that, we also Air Raid, Righteous Cause and Hand of A'dal as cheap spells to activate Kael'thas, leading to a free Libram of Hope. Its not like you're compromising a lot to have this combo, you're literally adding 1 card to high roll in some games. Also, Archmage Vargoth + Libram of Hope is VERY strong, even if by chance it heals an enemy unity. And of course Vargoth + any of the other cheap spells can be decent, especially with Hand of A'dal. 

1 Crusader out for Tirion 1 Sungil out For Murgur 

Two Imprisoned Sungill? Do you think is good enough? What about Murgur Murgurgle?