Guild Wars 2

If you start with T4 and then bring it down to T3 – it won’t get achievement done, just 1 tier of it, so you’ll have to do T4+T4 to complete.

I was hoping I wouldn’t have to do Tier 4 again, guess I will have to now

You just have to do the tiers in correct order (t3 then t4).
Unless you did not complete t3 you can do t4 as many times as you want, but it wouldn’t count towards the achievement.

I had all 4 tiers unlocked by doing Evon’s in order.
I switched over to Kiel and did them all in numeric order.
Just fine for T1 and T2’s achievement. But T3 did not give me credit. Doing T4 twice did give me credit for the achievement.