It is only in late games that these issues pop up.  Just has an epic 2v2 on Exile, 2 TBs vs Reg. and Oak.  Game had lots of swings showing a good balance in class and damg.  The issue came up around the 50min - 1hr mark.

1.)  Ashkandor and Mageslayer make regulus OVERWEHLMING powerful.  EDIT: (with only Ashkandor and Mageslayer, by lvl 15 Regulus deals 688 damg a second, NOT including critical hits,which hit for 1.5 -2k.  Tested it out last game as Regulus. 5/3/09)  At the very end, we were standing in our base next to our crystal firing at reg, freezing him, rain of ice, etc, and still he drained our heatlh (while we were next to the crystal) killing us while he remained at relatively full health.   This is due to crits + life steal + attack speed.  This combination make regulus unstopable when he has Ashkandor and Mageslayer.  Add in some other rings and attack speed items and there you go.

I challenge anyone to win a game vs regulus with that comination (conquest).

This shows that items favor melee based attacks.  You can only get 2k-4k crits off of melee attacks but NOT off of magic attacks.  Meaning, the team with the better items and melee attacks will always trumph the team with the same or better items and magic attacks.  There is no way a magic caster (TB), can win without items that allow him to crit with magic spells.

1.) Solution:   I suggest either reducing the elements in those items or.....

1.) Better Solution:  Add items that allow +crit% for magic casts. 

Now the Oak is killable even with those items.  He has to close into  range to deal the damg, then run when he gets low on health.  Regulus shoots from 6 away, making it much easier for him to escape or chase down enemies.  Don't get me wrong, Oak is bloody hard to kill as well, but at least we can drain his life and kill him with teamwork.  Even under the Regen crystal, both of us COULD NOT kill regulus with his item comination.

2.)  Citadel upgrade -time% DG dealth penatly.  You can fully upgrade it to knock off 40% of the time penalty when you DG dies.  Broken, as in, we had it maxed and still had to wait 25+ seconds to respawn.  Why even both sinking money into it if it doesn't work!  (EDIT:  Someone did the math and at lvl 20 it does work, just that the penalty is 60seconds)  Still is a worthless upgrade unless you constantly die as the Oak to use his reincarnation.  Should be replaced with a more useful upgrade or increase the % downtime.

2.) Solution:  Fix it so it actually works.  (EDIT: see above)

2.) Better Solution:  Who actually puts money into that? No one wants their DG to die, b/c when it happens, the game can swing the other way.  Instead of -10%, -20%, -40%  (which don't work mind you), double it.  Have it around -25%, -50%, and -75%.  That would make it more worthwhile.

Please feel free to add any late game issues you have seen or comment on solutions.  If you want to flame, I suggest to you, test these out.  They are real.  #2 is a broken issue while #1 is more serious.  There is no way to beat that combo.  Heck, I used to use it on light side.  I truely believe adding +crit% items for magic users would fix that imbalance.  As it stands, melee users will always win vs magic users if they both have the same items.