ideal riven = multishot + heat + fire rate / status chance
best faction mod replacement is fire rate if u have status chance riven, or [Blaze] if u have fire rate

pure heat config (when vs unarmored or with strip):
swap corrosive mods and merciless for [Blaze] + [Serration] + shotgun vendetta

beams use multishot twice on status dmg basically so this gun is op as fk https://warframe.fandom.com/wiki/Multishot

also note that corrosive multiplies heat dps by ~5x again on armored targets

here is my heat calculator https://docs.google.com/spreadsheets/d/1Ij97uMcfVN0ACybqgJZwT1e9LqkuE9bcjp8E69gaNfk/edit?usp=sharing
highly recommend you to check a potential riven or riven build before you invest in it to see if it is better than just using [Phantasma] or something