The best replacement for swarm is k9 unit.

The best alternatives to swarm are rated as following:
★★★★★  k9 unit
★★★★  bouncer
★★★★  hot head
★★★★  technician
★★★  guts
★★★  flame body
★★★  technician scizor
★★★  ninjini
★★★  tree rex
★★  poison point
★★  thumpback
★★  crusher
★★  k9
★★  holo targeting
★★  eye brawl
★  scoreloop
★  wings of liberty
★  holo
★  wind blast
★  bee hive
★  company of heroes 2
★  haunt
★  termite swarm
★  typhoon
  x flight
  ben 10 race against time
  hive

Your alternative for swarm is not listed? Suggest!
Speaking about swarm, one probably shouldn't forget about wings of liberty.

Other search terms related to swarm and their ratings are:
★★★★★ wings of liberty
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swarm
k9 unit
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