NZ's T20 batting problems might have seemed novel this series, but if you squint it's the exact same situation as the ODI side leading into the world cup. Lots of top-order batsmen and no finishers.
Finishers' job is to a) be willing and able to hit from ball one (Klusener etc), and b) know how to pace an innings, marshal a chase, when to nurdle and find 2s and when to hit big (Dhoni, Chris Harris, McCullum back when he batted 7).
In the ODI side we eventually settled on Neesham (yes to (a), getting better at (b)) with a side serve of CDG (yes to (a) as long as bowling isn't top tier, no to (b)) and a little help from Santner (hit and miss, shouldn't bat above 8). That was the best we could do because while not great, everyone else we tried ****ing sucked at finishing innings.
… and that's still the case in T20s, the newly recruited players for 5/6/7/8 haven't played the innings we need. But it's even worse in T20s because with the shorter innings you need even more players with these skills e.g. it's far more critical that your number 5 can do this in T20 than in ODIs.
Part of the problem afaics is that domestically, any young talented batsmen, including wk-batsmen who in times gone by would bat 6 or 7 and learn to play this role, now bat top 4 instead.
