The top champions outside of lane to counter Ivern include Aphelios, Kalista, and Zeri. These champions are all good at countering Ivern with high win rates over 62%. Even if these Ivern counter picks are not used in the same position as you, it's not smart to choose him into any of these matchups. They will very likely crush Ivern.
Conversely, if the other team choses either Rumble or Ziggs, Ivern mains should strongly think about taking him, as he easily wins against these champions with win rates over 55% against each ofthem.