What are some typical defenses (AC, Fort, Will, Reflex) for a defender at the different tiers (Heroic, Paragon, Epic) of a D&D4 game?
D&D Essentials is part of D&D 4th edition, and makes no differentiation as to source of feats. As essentials is entirely compatible, any character may take feats, utility powers (if appropriate), and items from the essentials books.
Check out this question.
However, it is important to note that the inclusion of any book or suppliment in an RPG is always subject to DM discretion, and so your DM may choose to disallow the book for any reason.
As a point of order it is not appropriate to give characters the new and improved expertise feats for free. Looking at the math here, DMs can draw their own conclusions about versatile expertise being necessary. The additional abilities granted by the new expertise feats, like ignoring cover, scaling damage, free actions to reload crossbows, and others, are beyond the scope of a simple math fix.
The tier system was introduced in dnd-4e, and is a more formal development of ideas from earlier editions.
Heroic tier: Levels 1-10.
Characters may have impressive skills, but operate on a basically human level.
Adventures take place in local environments - dungeons, towns, forests.
Threats are mostly part of the local ecology, or summoned or created. (Natural creatures, other sapient species, created mechanisms, plants.)
Paragon tier: Levels 11-20
Characters now have extreme, near-superhuman levels of their lead skills. They can accomplish things no ordinary human could (and make very difficult skill DC rolls!)
Adventures take place in a wider arena. They may save entire kingdoms, not just local villages. Their growing reputations will make them major players, even if birth and rank don't. They might lead guilds, be involved in court politics, or command soldiers.
Enemies also exist on a larger scale. Extraplanar threats become more common, and less likely to have to be summoned first. Players may meet dragons, invading warlords (and their armies), elemental or demonic creatures, colossal magical beasts.
Characters gain powers from a 'paragon class' - a development of the 'prestige class' idea from D&D 3e. The paragon class gives tightly-focused powers related to a specific concept of how to play the character's main class. (For example: A druid who specialises in driving animals berserk. A warlock who steals life from opponents. A barbarian who becomes more and more like a bear.)
Epic tier: Levels 21-30
Characters can accomplish awesome and impossible things with skills alone, before they even bother to use their class powers. Which are increasingly powerful.
Adventures are routinely extra-planar - if the characters even make their homes on their original world any more - and threats are ancient dragons, powerful planar entities, titans, or the like. Entire worlds or areas of existence may be at stake.
Each character progresses towards an 'epic destiny' - chosen by the player at L21. They gradually gain extra powers appropriate to this destined ending. (For example: becoming a god, or a transcendent energy-entity, or a heroic legend, or an immortal traveller.)
This effectively gives the GM 10 levels notice to plan the character's heroic final fate at level 30, which is where D&D 4e ends.
(The system has developed from a concept present even in very early versions of D&D, that a high-level character would eventually become immortal. The BECMI D&D is the first version with this idea, providing for immortality after level 36. Later editions had the concept of 'Epic levels', beginning at level 21. This progression tended to be slower than at levels 1-20, but to allow otherwise impossible feats, and continue to immortality. In D&D 3rd edition, Epic levels were 21-40, and Deities and Demigods provided limited rules support for becoming gods at levels 41-60.)