As a jungler trundle has always existed in that zone where they're not bad, but they aren't very good. Trundle was always fun, and was a good counter jungler, but most people played him top.
Why was trundle good top? well, Trundle had amazing sustain with his passive, which has been kept the same, now kings tribute, every time a minion dies around trundle, he gains a percentage of their max HP back. Trundle was also extremely strong in a duel do to his stat sapping nature.
Jungling
Jungling as trundle wasn't very effective because it was his ult that gave him that really strong 1v1 potential, and certain junglers could just make his day hell, out gank him, and take his stuff. It was a general pain to say the least.
Trundles ganks weren't necessarily 'weak' so much as situational, his Pillar was really good at cutting people off, or bumping people into others, but at the time it was his only slow, and the enemy had to be slightly pushed or trundle had to get it in a really good spo…