My first playthrough I overused Ike early on and had to basically let him "sit out" so my other units could get some EXP.  It's just so easy to watch him tear through enemy after enemy...

You are full of crap.

Haar > Jill.  Easily.  Here are the statistical averages (ignoring good/bad RNG):

58 vs 52 HP.  Haar wins.
38 vs 35 Strength.  Haar wins.
7 vs 10 Magic.  Jill wins but who cares, they don't cast spells.
38 vs 34 Skill.  Haar wins again.  Guess he is more accurate.
30 vs 35 Speed.  Jill wins... but they both usually double attack anyway so yay.
25 vs 35 Luck.  Jill crushes Haar.  Good thing it's only luck.
38 vs 33 Defense.  Haar owns Jill.  Defense is what keeps you alive against like 80% of the game's enemies.
16 vs 22 Resistance.  Jill's true value is this stat IMO.  It's what makes her good.

Haar can take more of a beating and give more of a beating than Jill can.  Heck, Haar is capping Strength at 38 when Jill only has 31.  He caps it a full 8 levels before Jill and 3 points higher too!

The only reason to ever choose Jill over Haar IMO is for her Resistance stat being so much higher than Haar's (usually).  That's why I took Jill to End Game instead of Haar but... it was a painful decision to make considering how awesome Haar is.

Even the worst of Radiant Dawn would be amazing in other Fire Emblems.  Every unit in Radiant Dawn turns out fantasticly at the end.  The only reason not to use a unit is if it takes too many resources to level (Meg/Fiona).

You sure talk big for someone who is wrong (full of crap). First thing. Jill will cap every stat save for 1 or 2. In my game I didn`t use Bexp on her and the only stat that wasn`t green was Def at 33. Right... Your personal experience is, of course, much better than the facts WoW posted. 

Haar will likely cap Str, Skill and DEF. Why is capping skills important? WoW is talking about average. Capping is irrelevant. 

Speed is more important than Att and DEF (considering that Att is Str + Weapon might) and Jill got that. Why is speed more important then Att or Def? That makes little sense to me... I love quick units, but in most cases (in  RD at least) 5 more attack could differ from 3 to 8 damage (whereas doubling instead of singling would only give 6). They're at least equally important - I'd say attack/Def is more important. 

Haar can double most things in the early chapters, but not as much in the endgame. After 3 playthroughs (on Normal/Hard) he has always been doubling in the end. Could, of course, be lucky RNG

5 extra Att won`t make a lot of difference against a Dragon with 44 DEF, especially when you can`t double him. Makes no sense. Against a unit with high DEF, att means extra much. Why? 47 att would give 3 dmg (and doubled 6 dmg), whereas 52 would give 8 dmg (17 doubled)

¨Also, ask anyone which one is more important Speed to counter double attacks or defense? I would rather take +5 speed than + 5 def anyday. Already commented on this. 

That is why Ed, Shinom and Rolf shine so much in the endgame. Even with a defense 10 points lower than Gatrie, they would survive a boss attack (no double). All units should manage to survive a boss attack, unless you've seriously messed up and brought some under-leveled units. If you have a unit (other than healers and mages vs melee) that dies vs a boss (1 hit), you shouldn't have taken him along. 

For Haar getting attacked by a magic user is deadly especially when he is doubled. Endgame is full of magic dragons and those annoying spirits with infinite range. The spirits have a very low speed, and so do the dragons. Haar easily doubles the dragons, and neither Jill (maybe if capped) nor Haar double the spirits. 

In my game Haar capped Res and I still find prefer Jill. Her high luck will help avoid hits and get criticals (she got 30+ avoid and 7+ dodge than Haar). My Haar was RNG blessed and Jill still outclassed him. In the end saying Jill is beteer than Haar is like saying 10 is higher than 9.9. I really doubt your Haar was RNG blessed...

As for the accuracy part, you have no clue. Hit is determined by several factors, not skill alone. Jill hit is a little bit higher than Haar when they are on the same terrain, equip the same weapons and are on normal byorhythm. Jill Byo has a little advantage over Haar (she spends more time on normal and less time on worse and best than him). I always thought all bios were equal, just differing from what playstyle you use. Also, what else inflicts hit then? I was almsot certain it was skill (no other abilities). Give some proof that it is not the case, or stop claiming people have no clue. 

Overall, I'd say you posted some personal experience, with little/no facts. You have no right to say WoW has no clue.

I wouldn't worry too much.  He appears in 4 chapters prior to the End Game scenarios which basically gives you almost no time to level him up or really get that much use out of him at all.  It's sad that he's gone and not having him available might make 1 or 2 chapters a tiny bit tougher but he's not critical.

Wow.  Oyv said almost everything I would have.

I will mention Biorhythms though.  I read a long while back that male characters tended to have smaller but longer rhythms while female characters tended to have stronger more erratic ones.  Basically this means that female characters get more of a bonus or penalty from biorhythm but their rhythms change around much faster.  Conversely male characters aren't affected by it quite as much but they tend to be affected for longer in each direction.  I never paid too much attention to biorhythm except when it was really bad though.