I've been looking at the heavy armor option.
I think my biggest hangup is thinking the character will need a good con for the extra HP's in order to survive melee. I can see that there is very little differance (2hp and 1 surge) between a 12 and a 14, but I'm having a hard time accepting it.

Having not played 4e beyond the lowest levels I haven't grasped that paradigm shift yet. hehe.
That and the character I've been toying with is a dragonborn ranger and I don't want to trivialize the healing surge bonus.
The Ranger in our group bumps Dex and Str and uses Light armor.
She attacks with a Longbow most of the time, then only goes to melee when necessary.
The hit points and healing surges matter less then since she is not in melee as often. She took the Melee Ranger path which also boosts hit points.
The downside is that she has to take feats for both ranged and melee, but there really are few important feats for one or the other. Most feats are Meh anyway for her, so this helps fill out her feat list.
But, she is really a TWF Ranger who typically doesn't do that until part way through an encounter (sometimes not at all).
The advantages of doing it this way are:
1) She gets to use cover more often.
2) She gets to wipe out bloodied foes from across the field early on.
3) She doesn't need as many hit points or healing surges.
4) She can protect the squishier back rank PCs anytime by just switching over to melee.
5) She is one less PC that the Cleric typically has to use Healing Word on.
6) This incentivizes enemies to attack the higher AC Paladin Defender (who does have more healing surges) instead of splitting their attacks between two PCs.
7) If the situation calls for it, she can immediately become a front line melee combatant (even at the beginning of an encounter).
Downsides of this are that she won't be using her Paragon Path Encounter powers early on in combats and she also doesn't give flank to the Paladin that often. On the other hand, often having just one melee attacker in the group makes it easier for him and the Wizard to coordinate the Wizard's AoE attacks on multiple enemies attacking the Paladin. Only the Paladin has to move out of the way.