- Minato needs kunai to teleport, they get destroyed by bijuudamas or gedo mazou chakra blasts
- Obito can teleport too, or rather he can teleport directly inside the avatar
- Chakra rods can be spammed & without info on what they do minato won't think to constantly dodge them, he will try to defend at some point
- he doesn't "need" kunai to teleport, only things that are connected to him or his chakra. Besides, in BM minato has the strength to hurl Kunai's a mile away from the battlefield. How far do you think Minatos kunai will fly if he smacks it with one if his tails? Not that minato doesn't have markings elsewhere in the first place U_U. He can teleport to clones too or even the ground he's touched. And since the location is by the ocean he can just throw a kunai into the water.
- lol, the avatar is very much physical and only the Jin (ie BM minato and BM Naruto) have shown the ability to allow someone to enter it. Obito teleporting inside is just a baseless assumption. That's like saying Obito can teleport inside killer bee in BM. When I see him teleport inside another being then I'll believe it. And even if he could, that means he'd be directly in contact with Minatos chakra which means he can instantly teleport to him and slice his head off (you must think Obito is real stupid).
- chakra rods can be spammed according to you right? Because I never saw them spammed. I'll tell you what can be spammed - FTG. Another baseless assumption, saying minato won't dodge an attack flying directly towards him. He's very aware of what kushina's chains can do to a tailed beast, so him seeing chains/rods wouldn't take common sense for him to realise that they could be dangerous of touched. And even of they touch him, they won't drain all his chakra instantly, he can just teleport out of it as long as he still has chakra. Not to mention that minato can still use a space time barrier which will est up every projectile thrown at him. He can makes barriers large enough to consume a tailed beast bomb and Juubi tailed beast bomb, so chakra roads aren't getting anywhere near him.