Couple things from my own meandering experience:
Lobo vs. Batman is definitely even. Why? Well, for one, Lobo has great damage. He wins the damage race every time. For another, once Lobo gets a hard knockdown, Batman has to guess between the overhead, the low, or the grab. Both the low and the overhead can stuff wake-up slide and using parry is guesswork at best. Slide can beat the grab, but if he doesn't do the slide, you'll find yourself knocked right back down again in the same shitty situation. To put it another way, if you factor in Lobo's damage with the fact that a lot of his stuff ends in hard knock downs, you get one of the worst situations in Injustice. Guessing wrong on a knockdown against Lobo means half of your life or more is gone and THEN you're put BACK in the same situation.
Any more experienced Batman players can correct me if I'm wrong.
With Doomsday, its true that he has MB Venom to come in. MB Batarang can beat that out, but the larger point is that you have to spend meter to keep him out and he has to spend meter to come in. I think that's probably part of why its an even match-up.
I could be wrong, though.