Early game Downgrades:
Brutal Tide can be used instead of Grim Fury I personally like Grim Fury Better, but You could definitely focus on some of the V polarities first (1 less Forma)
Fury can be used instead of Primed Fury (1 less forma) (Note that Berserker Fury is better than Primed Fury if you are consistently killing enemies.
Gladiator Vice can be used instead of Quickening or Primed Pressure Point Can be used instead of Condition Overload (1 less forma)
Primed Reach for Reach or Spring-Loaded Blade (Not recommended due to low status chance, but will work if using it to kill everything)

 Other options if you dont have the above mods:  

(Note Blood Rush is not replaceable, and I dont recommend replacing Shattering Impact unless going against non-armored factions)
Gladiator Might, Virulent Scourge, Sacrificial Steel, Body Count, Gladiator Rush, Drifting Contact

Recommended Forma/Upgrade order:
0 Forma: Brutal Tide, Blood Rush, Pressure Point, Organ Shatter, Quickening (Or Gladiator Vice), Reach, Fever Strike, Shattering Impact, Berserker Fury (Or Fury)
1 Forma: Brutal Tide -> Grim Fury (Personal preference. Skip if you like Brutal Tide
2 Forma: Fever Strike -> Primed Fever Strike
3 Forma: Reach -> Primed Reach
4 Forma: Pressure Point -> Primed Pressure Point and Berserker Fury (Or Gladiator Vice) -> Primed Fury (If you want
If you have Rank 5 Arcane Strike, Replace Quickening With Gladiator Might

Shattering Impact:
Shattering Impact is a very underrated and misunderstood mod.
Works on all enemies in the game except Archons.
It reduces 6 enemy BASE armor every time you deal impact DAMAGE to an enemy, not every impact status effect. This means 6 base armor per hit.
Because it reduces enemy base armor, it will always take the same number of hits to reduce a specific type of enemy's armor to 0.

 Enemy                        Enemy base armor values      Hits to 0 Armor
 Corrupted Heavy Gunner       500                          84
 Corrupted Lancer             200                          34
 Corrupted Butcher            5                            1
 Demolishers/Demolists        100-250                      17-42
 

From experience, bosses have relatively low base armor value, so they very quickly [Reach] 0

The Hirudo is a very fast weapon especially with Primed Fury and Quickening or Arcane Strike, so getting the number of hits required for reducing armor happens faster than you think.