I would definitely consider stuff like hybrid pen marks, hybrid pen masteries and blade of the ruined king instead of hydra. I've played a lot of shyvana myself (only in SR though) and I feel like these work better than the things you've mentioned.

I recommend you to verify your account in your profile because, heya, your Diamond and so you might receive more attention :)
Besides, you can visualize your guide a bit more by writing [[Doran's Blade]] to create this Doran's Blade with stuff like items or abilities if you want to :)

Good Luck and take my upvote!

So far this is a very short guide and I am assuming it isn't complete. I'd suggest adding a gameplay section that talks about how to play Shyvana both top and bot. Another good thing to add is when and when not to capture the points.

Overall it's a nice guide so far so it's a +1 from me.