I did not find where it's written in the rules that tarantulas have to fire on the closest target. I remember that this was stated in SMv2/TL rules but did not find it in any NetEpic codex (not in Squat or IG 5.2).
Actually, Squats list is one of the best competitive army lists.
Squat bikers are (too) great for the cost:
SM bikes 150 points for 5 , morale 2, break point 3, caf +2
Squat bikes 200 points for 7+1, morale 2 (1 while guildmaster is alive), break point 6, caf +4 (+5 for guildmaster)
SM cost per bike: 30
Squats cost per bike: 25 <- yes, better than SM and cost less
So at least increasing their cost up to 35 points per bike and rounding the detachment to 250 points would balance the bike detachment.
About praetorians, Leviathan are good for the price, they can easily replace an artillery detachment with it's Doomsday cannon and has some nice fire support ar 75cm.
Colossus is probably the best praetorian in squat list. I call it my swiss knife, it can do everything and do it well. First turn, place 4 missiles + 1 doomsday using gyro LoS, followed by a bunch of 4+/-2 hits.
Maybe a little adjustment on Colossus cost is needed. About Behemoth, when used with a Cyclop, it's terrible. Remove enemy shields with your behemoth and last hit with the cyclop

Behemoth is not that great but the railgun has a nice range and can hit easily.