This is not right in this absoluteness...
since you usually lose all the benefits of your secondary attribute with a proper race choice you can get very good results:
an eladrin fighter wizard is more than viable: good AC good mobility, very decent offense (fighter weapon talent and kensai focus longsword more than make up for your low low

int 18 and str 16
you don´t need implement mastery or fighter armor proficiency. You can do well enough without all those fiddly things.
i agree with this whole heartedly though in this example i would choose a Genasi over an eladrin but thats largely personal taste. many people make the claim that you NEED two classes that share the same stats and while that situation is optimal, its only really necisary to find two classes that might not be very dependent on their secondary stats.
A fighter wizard can actully work very well together and in this respect is an excellent example of why the hybrid rules are great so long as you map out your character choices; and in the long run and don't mind the possibility of having to wait a few level before your vision works fluently.
this is how i would use the hybrid rules to create an interesting and effective character.
====== Created Using Wizards of the Coast D&D Character Builder ======
level 5
Genasi, Fighter|Wizard
Hybrid Talent: Fighter Armor Proficiency
Arcane Implement Proficiency: Arcane Implement Proficiency (heavy blade group)
Elemental Manifestation: Firesoul
Firepulse: Firepulse Strength
FINAL ABILITY SCORES
Str 18, Con 13, Dex 10, Int 18, Wis 13, Cha 10.
STARTING ABILITY SCORES
Str 15, Con 13, Dex 10, Int 15, Wis 13, Cha 10.
AC: 23 Fort: 18 Reflex: 20 Will: 15
HP: 45 Surges: 8 Surge Value: 11
TRAINED SKILLS
Religion +11, Athletics +8, Arcana +11
UNTRAINED SKILLS
Acrobatics -1, Bluff +2, Diplomacy +2, Dungeoneering +3, Endurance +2, Heal +3, History +6, Insight +3, Intimidate +2, Nature +5, Perception +3, Stealth -1, Streetwise +2, Thievery -1
FEATS
Level 1: Hybrid Talent (armor prof)
Level 2: Elemental Empowerment
Level 4: Arcane Implement Proficiency
POWERS
Hybrid Fighter at-will 1: Reaping Strike
Hybrid Wizard at-will 1: Thunderwave
Hybrid encounter 1: Icy Terrain
Hybrid daily 1: Lasting Threat
Hybrid utility 2: Shielded Sides
Hybrid encounter 3: Probing Attack
Hybrid daily 5: Acid Mire
ITEMS
Cloak of the Walking Wounded +1, Scale Armor, Adventurer's Kit, Greatsword, Dynamic Longsword +2, Heavy Shield, Summoned Hide Armor +2
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