Runegorger, Riot!

My two cents? Just drop the mallet for an Aegis of the Legion.

Pretty decent guide. Your build seriously lacks mres, so I would consider a FoN or even Banshee's instead of the Wit's. It'll drop your offense a bit, but at the end of the day it's worth it. You can still get the Wit's as a utility item occasionally. Don't listen to the first guy, Randuin's is a very legitimate item. However, he's right that you don't really need that much GP10. Usually a Philo Stone is enough, but if you're getting a Randuin's it's fine to get a Heart of Gold too. Take 21/9/0 for masteries, in my opinion it's the best for Jarvan. Keep up the work on the guide, and it could be good. You might want to consider an Aegis or some other item instead of a Mallet, however, since in many cases it is not cost effective/counter productive to get both a Trinity and a Mallet.

lololol the top guy said Randuins is bad, please uninstall now.

+1 decent guide so far

i agree with mikuroo on too many gold/10 items. philosophers stone should be fine. You grab a avarice blade but have no intention to build it into a youumu's ghostbalde. for masteries, 25/0/5 isn't the best layout. Could use a 21 on one side and 9 on the other.

Keep up the good work!

+1 good guide, and welcome to mobafire! : )
However, there are several things I can point out.

1. You have way too many gold per 10 seconds items. If you farm properly, you really only need give or take 1. Randuin’s is pretty bad, so drop heart of gold. However, philosophers stone is a really good top lane sustain item, and shurelyas is really good.

If you really really want yoomu’s, go ahead and take the Avarice Blade.

Masteries: I suggest you go either 21/9/0, for the extra 30 hp, and 108 hp at level 18. Do not go 25/0/5, you are a tank, 1.5% more damage won’t really do much.

Items section: It is a huge wall of text. Instead, you should use the list bbccoding, too make it neat and readable. Currently it is pretty bad looking.
Everything else you currently have is fine, but It is a pretty short guide, so I would advise you slowly add more sections.

If I helped, don’t forget to +rep!