Using that same technology wouldn't defenders be able to refract any laser attack away using lenses, and/or dissipate the heat of the attack? Or is there some way that laser technology gives an advantage to the attacker?

Neither. For the former: we can focus frankly absurd amounts of energy in small areas quite easily (we smelt tungsten pretty easily), but that doesn't imply that we could make something to survive that environment. There are two major issues here:

1. The attackers know precisely where all of there energy is going, and can keep everything perfectly aligned so that everything stays under material limits, whereas the defender has to deal with it coming in at any point from any direction, which is far harder.
2. The attackers can focus energy from multiple emitters on one point, whereas the defenders have to deal with all of the energy at the point it's arriving.

For the latter: the defences against lasers are much lower-tech than lasers: fundamentally, you just need to either put a bunch of stuff in the way, preferably reflective/shiny stuff, or move fast enough/unpredictably enough that the enemy can't keep their lasers pointed at you well enough to get through whatever stuff you have in the way. Neither of these require any particular technology.

Using that same technology wouldn't defenders be able to refract any laser attack away using lenses, and/or dissipate the heat of the attack? Or is there some way that laser technology gives an advantage to the attacker?

Neither. For the former: we can focus frankly absurd amounts of energy in small areas quite easily (we smelt tungsten pretty easily), but that doesn't imply that we could make something to survive that environment. There are two major issues here:

1. The attackers know precisely where all of their energy is going, and can keep everything perfectly aligned so that everything stays under material limits, whereas the defender has to deal with it coming in at any point from any direction, which is far harder.
2. The attackers can focus energy from multiple emitters on one point, whereas the defenders have to deal with all of the energy at the point it's arriving.

For the latter: the defences against lasers are much lower-tech than lasers: fundamentally, you just need to either put a bunch of stuff in the way, preferably reflective/shiny stuff, or move fast enough/unpredictably enough that the enemy can't keep their lasers pointed at you well enough to get through whatever stuff you have in the way. Neither of these require any particular technology.