This build sound strange to everry body but try it, it's simply amazing based on magic dammages, attack speed, magic penetratio and ****ing debuffing!!!

Magic Dammages:

you will deal a lot of magic dammage with items, Burnout and your E skill reduce your target armor of 15% and when u hit him it will deal dammages equal to the 20% of the skill dammage That means approx 55 magic dammages for hit.
Total magic dammages from items : Approx 165 (+20 malady +42 Wit's end +100 Madred's Blood razor considering 2,5 k of target healt)

Total Magig dammages from abilities

:55 each hit +90 everry seconds
BURNOUTIT WILL GRANT APPROX 90 MD each second.
Flame Breath: dont considering the initial 260 MD of the skill it will deal for 4 seconds 55 mg each hit
Dragon's Descendant: siply 400 magic dammages.

TOTAL potential Of Magic Dammages on hit:220+ 90 per second

PS:consider u will have something like 1.9 attak speed..

ATTACK speed

: simply necessary on her its reduce Flame Breath cd, buff burnout and charge your ulty .

Magic Penetration:

: yes guys mgic penetration is te secret of this build we just see how much magic dammage per second u will deal now with masteries and runes u will keep it real!!!

AND NOW DEBUFFING!

Shyvana is a great debuffer:
just think about-24 MAgic resist after 4 hits then think about -20 armor to all enemy in 1200 range area , and also your E skillwill reduce the target armor by15% (if you use it in the right moment in team fight after it will be an AOE effect!!!
ALL of this debuff stack really well with her abilitis it' simply amazing!!!!

I Know this is not a ful GUIDE ill finish it in the next days but please try IT and U will be surprised!!!!!!!