Unless you miss the paladin, or the paladin has something to attack you with at range (half-elf with Versatile Mastery and Eyebite, dragonborn with Hurl Breath, or even Quick Draw and a ranged weapon).
If you miss a paladin with a minor action, then you've got another minor action before you've touched your standard action or your action points. Which a solo has. And no, you shouldn't -auto hit-. That's not the point, is it? But if you hit often enough, with a power that has +3 to hit over the other powers -AND- targets a NAD, it'll do the damage you need it to do. Really.
These other things you mention are counterable with the beholder's -standard- action.
Fact is, a beholder is a controller, and should be using his control to... well... control the things that make life hard for him, like, say, a paladin who can heal everyone ad nauseum. How intellegent does a monster have to be to go 'That holy guy over there is healing this entire group of future slaves and saving them from my blasts of superiority. Maybe I should focus my fire on him. Maybe I should hold off on doing the things that heal his friends. Maybe I should -shut that guy down-.'
Hey, did you know the beholder can shut that aura off as a minor action?
All I hear is 'Ability too strong! Ability too strong!' and not enough 'But the monster countered with this....'
The broken part of the paladin-hospitaler combo, in this instance, from what I hear, is that the DM didn't bother to play the monster in response to it, and did not attempt to use the abilities available to shut the 'problem' player down.
An eye tyrant has the tools to deal with this situation. Period. Use them. Complaining that the player is broken when it is clear that you did not use the tools -designed to handle situations like this- is like a rogue complaining about his poor damage output because -he never bothers to flank.-