My favorite team is this one :
Ike
Soren
Boyd
Oscar
Rhys
Mist
Rolf
Nephenee
Kieran
Volke
Zihark
Jill
Basically, one of each type. I also take some units like Tauroneo or the Laguz heron prince (forgot his name) or Elincia for late chapters, to complete my party.
But these are the main ones.
And none of them are liabilities to me, as I master the strategy and tactic thing.
I think people prefer to say that some characters are bad instead of saying their strategy suck, like saying it's easy in the first chapters because they always use the same characters, and then they can't keep the weak ones alive without great luck and difficulty later.
I'm waiting eagerly for FE:RD, as it seems it's very good difficulty wise (I loved the hard mode) and it revealed all the people that were saying the game was too easy, but were all playing on Easy. Some people have no shame.
Like PoR, I'll play RD first in Normal, then in Hard mode for the second playthrough which reveals the true story.