Trundle is a buffer/debuffer (1v1) hero. His abilitis are focused on buffing him self with dmg and atack speed and debufing the targets defences and offenses so the main focus here is Attack dmg. and speed. mostly because his abilities are focused on (+ physical dmg)
All the items are placed right, you will have so much speed that frozen mallet is not necessary once you get tri ( the 25% chance to slow them) despite the ghost blade and your aoe curse ability being able to cath up is easy thats enough for your slow and as for the last item, cloak and dagger you get that only if they have too much CC, or if you want to experiment differently you can replace boots with mercurys and find another +speed item

AS FOR THE RUNES GO FOR AMOR PENETRATION, DMG, SPEED ,