There are some things manaphy can switch in on easily, but it'll still get worn down pretty easily due to that same basic typing you talking about, it has very little resistances and with TG sets having no recovery its not that hard to rack up damage on Manaphy. Also from my experience on wifi i realise manaphy can do massive damage to a team but alot of people are treating it as if it can OHKO everything after a TG, if anything I actually fear the Rain Dancer more than the Tail Glowerbecause it is harder to kill but by no means do i think it should be banned
Once it has rest it clear limits itself.It open self up counters because it can't carry ice beam and grass knot.