Picking up a term of Siilk here: Skycamping. Works like this: You roll out a vtol, or mech and narc enemies with it. Also you have an ELRM Shiva flying circles above the enemies head at ~1200m altitude. Rain down lrms, enemy hardly will find cover and cannot outrun them anymore. Takes down a Mad Dog in 2 slavos and is next to impossible to counter (being that we do not have an LBX10 Sulla yet....).
Mass Huits: Honestly, 3 or more of those can really ruin any kind of proper battle because they just mow away almost everything at very long range. 1 or maybe 2 of those as AA are okay, but by the time more are fielded you pretty much have to resort to arrows or LT, which blows.
Players switching teams to be on the winning team no matter what, also players who late join and join the winning team.