I know RangerWickett has responded and I think his fix should work, which should mean it has an interesting use (especially if your attack boosting abilities would work perfectly normally - as far as I can tell all they know is that a lot of effort was required to make that attack hit).
I love the way the mechanics of the power enforce the fluff.
While this is a legitimate point, it's rather moot if nobody ever uses it because of the fact it prevents a great deal of abilities that affect d20 rolls. For example, why would an Avenger ever want to use this (actually even with the proposed fix an avenger still wouldn't want to use it - but he would be a tiny corner case and therefore quite ignorable)? Why would a Warlord ever want an ally to use this (Remembering if they spend an AP, they get a substantial bonus to hit with their next attack roll)?
Put another way, at the cost of the Skyseer's minor action, you know with almost 100% certainty whether a power will hit or not when it is used.
This isn't quite true. A lot of conditional modifiers can apply on an attack outside of just the d20 roll - which as I noted this power can't apply any of them (because it's not strictly speaking an actual attack roll). In addition to this a lot of allies can affect rolls at the time to boost a hit (especially once you get into paragon and epic tiers) with immediate interrupts. By removing the attack roll effectively, the power removes the ability for most of those to trigger and thus makes it a very poor power to use on anything important - which can be salvaged in a remarkable amount of ways if you get high enough in level especially.
A really strong example is a Warlord with his ally (whoever that is) with this power. Would you personally risk using this with Lead the Attack? What if that Ally was a Warpriest? The Warlord gets up to the creature, rolls a 1 and just as he's about to sadface - REROLL THE 1 (often that dramatically in my experience) cries out from the adjacent warpriest and his reroll 1 power salvages the terrible attack roll. High fives are exchanged and a monsters pants are firmly pulled down around its ankles for a good hard heroic spanking (gee I'm getting hot and bothered already). In this powers case, same situation but the Warlord rolls it ahead of time thinking it could be handy. Whoops! Just boned your most important daily powers and the Warpriest can't save you - even though he actually totally *could* have done so.
Of course if it is explicit that it counts as the attack roll as if you had rolled it then, which allows all the above stuff to trigger on a missed attack (or just in general) like heroic effort, a warlords tactical presence and such forth it becomes a lot more useful - while still being pretty mechanically risky. It's also worth noting that you have effects in the game that work like this as well, such as dice of Auspicious Fortune.
Edit: I would like to point out - for the record - that I really like the theme and
especially love the daily power it has. I personally feel the daily power is worth the price of admission alone. It also has clearly got a lot of love in the thought process behind what the place of the theme in the world is and the supporting fluff it has. Something that I think Wizards could learn from. It is hard to judge the theme though, because themes aren't just an extra encounter power or a couple of features - but also about what they give you access to. A poor entry power doesn't matter if the later powers are awesome.