What you're missing is that Level 30 items, particularly Weapons/Implements, Neck, and Armor, are often 5+ or 15+ items. The items you mentioned exist, but they exist (in both cases) as 15+ items- i.e., you could get a +3 version as a level 15 item, a +4 as a level 20, a +5 as a level 25, and a +6 as a level 30 item. The GodplateDDI is just a Masterwork Armor type. In this case, Armor of NegationDDI is from Adventurer's Vault, and is a 15+, and the Weapon of the ConquerorDDI, also a 15+, is in PHB: Dragonborn. Very little out there is available as a level 30 and only as a level 30, and even less of it is good.
The other key thing is that higher level play isn't necessarily about new items, but about combinations. Frost WeaponsDDI are a 3+ weapon, but you could stick with them all the way through- in Paragon picking up Lasting FrostDDI as a feat, possibly WintertouchedDDI as a feat, Icy HeartDDI as a feat, Siberys Shard of Merciless ColdDDI (paragon), and Gloves of IceDDI (paragon), then grabbing the Epic versions of the Shard and the Gloves. Boom, once you've hit an enemy, you now are dealing a lot more damage to them than just the Frost weapon would indicate. Firewind BladesDDI (4+) are phenomenally abusable if you have a way to add to damage instances that aren't rolled and aren't attacks (see the Radiant OneDDI Epic Destiny, for example). Harmony BladesDDI and Reaper's WeaponsDDI (both 4+) are great ways to abuse crit-fishing- if you can get a way to double roll all your attacks, an expanded crit-range, and many attacks, you can spawn more off of critical hits. Radiant WeaponsDDI at 15+ give you not only a change to Radiant (check out the level 16 feature of the MorninglordDDI PP to find out why that's good), but also an Item bonus to damage, freeing up your Arms spot.
Just to turn away from melee strikers, for a moment, Shimmering ArmorDDI (4+) lets you avoid Opportunity Attacks. A Staff of Sleep and CharmDDI (3+) is a dream power for just about any controller wizard. And Ironscar RodsDDI (3+), Unforgettable CudgelsDDI (8+), and Crusader's WeaponsDDI (9+) make Dizzying MaceDDI builds come to life- or, in the latter's case, providing a Morninglord Controller a lot of room for awesomeness, no matter what powers they take.
There are a handful of items considered to be very powerful that only exist in a level 25 or higher form, and many of them are Rares (i.e. you shouldn't be getting more than one). If you have a way of negating immunity to poison, for example, the level 27 Sword of Black IceDDI – an Uncommon – is phenomenal – when you hit with it, you deal rolled damage, so you're basically getting additional damage instances (sadly of poison, but if you have a way to deal with that, you're golden). At 28, you have Boots of TeleportationDDI, giving you at-will teleportation (though some builds will have that already). And at 29, you have the 2 most powerful rings in the game, both Rare – Ring of Free TimeDDI and Opal Ring of RemembranceDDI. The former gives you extra actions (as many as one per turn) and a nice little resistance, while the latter gives a relatively broad Item bonus to some attacks and skill checks, as well as a daily power to regain another power, which is always great.
In short, high level play isn't really about the items- most of the best items are things you'll have picked up through Heroic and Paragon and still be upgrading, with a few supplemental great ones towards the end.