Tiberius has no damage fall off, meaning 650 damage every .7 seconds and .49 seconds no matter what range you're at. The best counter is someone like eminence Lian or a sniper who can deal more damage than Tiberius from afar.

Your heavy blade goes through reversal.

Pick up resilience for heavy blade, or it'll slow you for 3 seconds. You could also pick up someone like Atlas who can catch the heavy blade, someone like Zhin/Koga who can cleanse the slow, or someone like totemic ward Grohk to prevent the slow.

The trailer alone tips you off that Tiberius was made to counter Raum. Tiberius's heavy blade slows Raum, and his weapon shots shred Raum.