Yes, I know it will be expensive.
Question is.. will it be good?  I kept trying to find ways to stack +DEF, but it was always a small percentage on a deep bonus to like 2 damage types...  so I went for regen, instead.
For contrast, heres a soft-capped with 1 mob DEF build...  (At least, according to Mids)
Hero Plan by Mids' Hero Designer 1.81
http://www.cohplanner.com/
Click this DataLink to open the build!
Marcus Supertank: Level 50 Magic Tanker
Primary Power Set: Invulnerability
Secondary Power Set: Super Strength
Power Pool: Fighting
Power Pool: Fitness
Power Pool: Speed
Ancillary Pool: Energy Mastery
Hero Profile:
Level 1: Resist Physical Damage -  (A) Reactive Armor - Endurance/Recharge
 
-  (3) Reactive Armor - Resistance/Endurance
 
-  (3) Reactive Armor - Resistance/Recharge
 
-  (5) Reactive Armor - Resistance/Endurance/Recharge
 
-  (5) Reactive Armor - Resistance
 
-  (7) Steadfast Protection - Resistance/+Def 3%
 
Level 1: Jab -  (A) Mocking Beratement - Taunt/Recharge/Range
 
-  (36) Mocking Beratement - Taunt/Recharge
 
-  (36) Mocking Beratement - Taunt
 
-  (36) Mocking Beratement - Accuracy/Recharge
 
-  (37) Mocking Beratement - Taunt/Range
 
Level 2: Temp Invulnerability -  (A) Reactive Armor - Resistance/Endurance
 
-  (33) Reactive Armor - Resistance/Recharge
 
-  (34) Reactive Armor - Endurance/Recharge
 
-  (34) Reactive Armor - Resistance/Endurance/Recharge
 
-  (34) Reactive Armor - Resistance
 
Level 4: Dull Pain -  (A) Panacea - Heal/Endurance
 
-  (45) Panacea - Endurance/Recharge
 
-  (45) Panacea - Hea/Recharge
 
-  (46) Panacea - Heal/Endurance/Recharge
 
-  (46) Panacea - Heal
 
-  (46) Panacea - +Hit Points/Endurance
 
Level 6: Resist Elements -  (A) Gladiator's Armor - TP Protection +3% Def (All)
 
-  (7) Reactive Armor - Resistance/Endurance
 
-  (9) Reactive Armor - Resistance/Recharge
 
-  (9) Reactive Armor - Endurance/Recharge
 
-  (11) Reactive Armor - Resistance/Endurance/Recharge
 
-  (11) Reactive Armor - Resistance
 
Level 8: Unyielding -  (A) Reactive Armor - Resistance/Endurance
 
-  (13) Reactive Armor - Resistance
 
-  (13) Reactive Armor - Resistance/Endurance/Recharge
 
-  (15) Reactive Armor - Resistance/Recharge
 
-  (15) Reactive Armor - Endurance
 
Level 10: Haymaker -  (A) Mako's Bite - Accuracy/Damage
 
-  (40) Mako's Bite - Damage/Endurance
 
-  (40) Mako's Bite - Damage/Recharge
 
-  (40) Mako's Bite - Accuracy/Endurance/Recharge
 
-  (42) Mako's Bite - Accuracy/Damage/Endurance/Recharge
 
-  (42) Mako's Bite - Chance of Damage(Lethal)
 
Level 12: Resist Energies -  (A) Reactive Armor - Resistance/Endurance
 
-  (17) Reactive Armor - Resistance/Recharge
 
-  (17) Reactive Armor - Endurance/Recharge
 
-  (21) Reactive Armor - Resistance
 
-  (21) Reactive Armor - Resistance/Endurance/Recharge
 
Level 14: Boxing Level 16: Tough -  (A) Aegis - Resistance
 
-  (25) Aegis - Resistance/Endurance
 
-  (25) Aegis - Resistance/Recharge
 
-  (27) Aegis - Resistance/Endurance/Recharge
 
-  (27) Aegis - Endurance/Recharge
 
Level 18: Invincibility -  (A) Luck of the Gambler - Recharge Speed
 
-  (19) Luck of the Gambler - Defense
 
-  (19) Defense Buff IO
 
Level 20: Knockout Blow -  (A) Basilisk's Gaze - Accuracy/Hold
 
-  (42) Basilisk's Gaze - Accuracy/Recharge
 
-  (43) Pounding Slugfest - Damage/Recharge
 
-  (43) Pounding Slugfest - Damage/Endurance
 
-  (43) Damage Increase IO
 
-  (45) Damage Increase IO
 
Level 22: Weave -  (A) Luck of the Gambler - Recharge Speed
 
-  (23) Luck of the Gambler - Defense
 
-  (23) Defense Buff IO
 
Level 24: Swift Level 26: Health -  (A) Numina's Convalescence - Heal/Endurance
 
-  (37) Numina's Convalescence - Endurance/Recharge
 
-  (37) Numina's Convalescence - Heal/Recharge
 
-  (39) Numina's Convalescence - Heal/Endurance/Recharge
 
-  (39) Numina's Convalescence - Heal
 
-  (39) Numina's Convalescence - +Regeneration/+Recovery
 
Level 28: Rage -  (A) Gaussian's Synchronized Fire-Control - To Hit Buff
 
-  (29) Gaussian's Synchronized Fire-Control - To Hit Buff/Recharge
 
-  (29) Gaussian's Synchronized Fire-Control - To Hit Buff/Recharge/Endurance
 
-  (31) Gaussian's Synchronized Fire-Control - Recharge/Endurance
 
-  (31) Gaussian's Synchronized Fire-Control - To Hit Buff/Endurance
 
-  (31) Gaussian's Synchronized Fire-Control - Chance for Build Up
 
Level 30: Tough Hide -  (A) Luck of the Gambler - Recharge Speed
 
-  (33) Luck of the Gambler - Defense
 
-  (33) Defense Buff IO
 
Level 32: Stamina -  (A) Endurance Modification IO
 
Level 35: Unstoppable -  (A) Recharge Reduction IO
 
Level 38: Hasten -  (A) Recharge Reduction IO
 
-  (50) Recharge Reduction IO
 
-  (50) Recharge Reduction IO
 
Level 41: Focused Accuracy -  (A) HamiO:Cytoskeleton Exposure
 
Level 44: Physical Perfection -  (A) Endurance Modification IO
 
Level 47: Taunt -  (A) Mocking Beratement - Accuracy/Recharge
 
-  (48) Mocking Beratement - Taunt/Recharge/Range
 
-  (48) Mocking Beratement - Taunt/Recharge
 
-  (48) Mocking Beratement - Recharge
 
-  (50) Mocking Beratement - Taunt/Range
 
Level 49: Super Speed ------------
Level 1: Brawl Level 1: Sprint Level 2: Rest Level 1: Gauntlet 
Level 4: Ninja Run 
Aren't we permitted two builds, now?  Could one have both the first build for soloing and the second build for tanking?