Honestly Rageblade would be a healthier item without Phantom On-Hit (+Rework Idea/Suggestion)
##Direction
In exchange of removing Phantom On-Hit, Just buff the stats it already offers and maybe add Physical On-Hit damage alongside the Magical On-Hit damage to match it's current Hybrid niche.
##Idea/Suggestion
Guinsoo's Rageblade
+50 Attack Damage +50 Ability Power +50% Attack Speed
- UNIQUE PASSIVE: Gain bonus 15 - 30 Physical and 15 - 30 Magical On-Hit Damage (based on level).
- UNIQUE - Last Whisper: Gain 6 - 15% Armor Penetration (based on level).
- UNIQUE - Dissolve: Gain 6 - 15% Magic Penetration (based on level).
##Thoughts of Guinsoo's Rage
Guinsoo's Rage Passive existing on top of everything that already got buffed would be too strong in my opinion, however if it is required to remain for whatever reason then I propose this instead...
- UNIQUE: Basic attacks grant a stack of Rage for 5 seconds, after 5 successful basic attacks, gain Guinsoo's Rage.
- UNIQUE - Guinsoo's Rage: Attack Speed Cap is temporarily removed while Guinsoo's Rage is active.
##The Goal
The goal of this is to allow it to offer more of a Mixed DPS Hybrid dream that it's suppose to have.
Buffing the stats would no longer be a drawback to some champions in the early game, while still retaining it from being incredibly strong and rushable by keeping the Passive Stats scale with level. Additionally with such said changes this item could open up to a lot more champions who don't usually try to enhance their magic damage due to the physical being more overall effective.
Some Examples of Champions who could possibly use the item with such changes...

And such changes also shut down the dominance that some Champions have over others who might use the same item...

Something like this be sick