hmm.. meh ? i guess that you dont have IBAT zetad and this is why you are saying this.
it is not the best zeta out there obviously, not when Zinn around and R2 NC is around aswell. but its top5 for sure. why ? simple. every turn he give himself 20% TM, and give other allies 10% TM.
surely not meh. add this to the fact that he attack a lot outside of his turn, and he can be called for assist, and it give you at least 100% More tm overall to him, and 50% more TM overall to his allies in an ARENA battle, at least. i could win the Meta team of CLS, R2, zHan, Thrawn, GK if their modding was only slightly superior than mine, or equal/worse. since i zetad on IBAT, i can win this meta team when god-tiered mods, without RNG involved even.
this is an excellent zeta, if you talk about arena.
GW and TB also very useful, and in P1 hAAT is very hard to solo WITHOUT the IBAT zeta. thats because it jumps his speed so good. example on my CLS, 261 speed. without zeta ? his speed every turn is 261. his speed every turn when IBAT zetad is 261/0.8 = 326. now, tell me that you wouldn't zeta an OP toon if it would say "60 more speed to him and 20 more speed for others" (my han is 222, for example, and if every CLS turn he get 10% tm, he need to fill 90% TM at the speed of 222. which means, 222/0.9 = 246.)
IBAT is surely amazing zeta for Arena, TB, GW, Raids... thats all. good luck with that info.