WotR Sealed is fine. Don't get me wrong, the Gandalf deck is good, but it is by no means invincible. Aragorn can handle it easily as Aragorn can kill a nazgul with a sword and
Pledge of Loyalty (plus one exertion). If you don't flood the pool, that's an easy double. I am assuming
Riders in Black still isn't working-that would make the Nazzies that bit tougher. Eowyn is solid as well, as it comes with some good pumps. Just don't play six companions, lose them and take burdens from
Drawn to its Power. The Legolas deck is terrible, though.
The Gandalf fellowship is good, but can have trouble finishing minions off. This makes doubling difficult-play some minions that won't die, and hold enough cheaper ones in hand for a swarm. The important thing to work out is whether to go for Gandalf or Frodo based on the pumps already used.
As for
Stragglers, you do really need the Mouth of Sauron deck in Series 2 to get set up properly. This means you miss out on Saruman who I find terrifying. Uruks played well are just as good as
Stragglers, and you get them one series earlier.
To beat
Stragglers you need to be able to kill and have strength pumps. Rohan with swords and spears is best at killing, but Aragorn does it nicely as well with the damage +1 from the swords. Legolas is still terrible. I find
Stragglers to be most effective against the Hobbit set up: more reason to try something else. Gandalf supporting Rohan is great fun, though.