I play him in top lane, so it's a little bit different for me...
This is what I build:
- I rush a chalice for that crazy mana regen. This way I can spam my Q harrass and stay in lane forever.
- I build boots 1, then glacial shroud, then boots 2 (either tabi or mercs)
- I build wit's end after that (I know you don't include it in your build, but I like the ST damage, AS, and MR on it)
- Then I'll usually finish up my Frozen Heart (that 20% AS debuff is pretty strong, don't underestimate it! And the 99 armor is awesome too.)
- At this point, I'm extremely tanky, so I'll probably build phage then ionic spark. Then build phage into frozen mallet.
- After I have boots 2, chalice, frozen heart, frozen mallet, ionic spark, and wit's end then I look for what I want to replace chalice with (if I haven't already replaced it that is...). Spirit visage is a good option to make up for the 30 MR that you lost, but remember it's always situational.
For jungling, you'll probably want something more like this:
- Boots (of course)
- Ionic Spark (WW is a slow jungler, he needs something to clear faster and since you're not getting wriggle's this is probably something you'd want early)
- Phage (to help with ganks when you don't have red buff... hopefully your ganks will be successful with just your ult, but the slow from phage is there just in case. 5 hits from your ult almost guarantees a slow)
- Boots 2 (tabi or mercs)
- Glacial Shroud
- Spirit Visage (depends on if you really want it now or not)
- Finish Frozen Heart
- Finish Frozen Mallet
- Situational (I would suggest an attack speed item, preferably wit's end for MR)
- If you don't get Spirit Visage then some other viable options would be:
a. WotA (your Q does %HP damage, WotA will make you heal even more plus buff your AP carry)
b. MBR (against health stackers)
c. Aegis (depends on your support)
d. Black Cleaver / Starks (make your AD carry stronger, and possibly your jungler if you had an AD jungler; IDK about the new stark's though)
e. Void Staff / Abyssal Scepter (For extra MPen... Abyssal is probably better due to it's aura and MR)
Those are my thoughts, but I'm not an avid WW jungler so I wouldn't know, hope I helped
Late game, you can literally 1v2 or 1v3 unless they have boatloads of CC. And even then, you're tough to take down!