Certainly not ...
Combat log tells you at best wich numbers you rolled (and as you mentioned its far from perfect itself) ... you never find there what could you do to improve your hit chance, and you especialy cant find there any tip before you land (or rather miss) your strike, since log is by its very nature "loging" what allready happened, not what will happen in next few moments. :-/
If your "target percentage tooltip" tells you you have 60% chance to hit ...
As new player with little to no clue about game mechanics (since you obviously didnt read tutorial tips

) you will be like "oh shit, this isnt much ... well, lets try and hope" ... wich can be source of lot of frustration.
BUT!
If your "target percentage tooltip" tells you: (numbers are only example, take them with reserve)
Weapon proficiency -
X - 10%Target in range -
X - 10%Target visible (in terms of light) -
X - 10%You clearly see that if you switch your weapon for some your character is proficient with, you take another few steppes closer, and you somehow deliver light source to your target ... you sudently raise your hit chance from 60% to 90%.
//Edit:
Note that i would also expect this tooltip to be pinable, just as many others allready are ... so player who would see those three red
X should be able to pin it ... and mouseover then to see that "proficiency means blah blah blah ... to incerase your chance to hit, equip weapon you are proficient with" ... etc.
