I've faced an army like the one you have their at 1850pts and I can safely say that I often was disappointed by two of his units:
-dreadnought, mm+hf in drop pod
-land speeders, mm+hf
Each time, the dreadnought and land speeders died, as I made them my priority targets. While this did draw firepower away from his other units, you must consider what his other units were:
-1 TL-lascannon razorback
-land raider (lascannon pattern)
Despite him have a decent amount of anti-tank in the rest of his force, nothing in his army really put a huge pincer on me from turn 1, as all his most dangerous units (assault termies, vindicator, land raider in your case, sternguard in razorback) were close ranged, and so I could spend my 1st turn removing the speeder+dreadnought. After the alpha strike, I was able to watch him slowly move towards me with the other units, allowing me to react with deep strike/mechanized units (I had a chaos space marine army list).
If you take the bikes, it will make many players nervous, as they will have to divide firepower over to a unit that can severely damage them while also not being an easy target to kill. Additionally, you can hide your bikes near the land raider, and can pop transports to give your terminators friends to play with right when they jump out of the land raider.
Additionally, I think that the land speeders may have survived if they had not been the only fast melta in his army besides the dreadnought.
I don't think that the dreadnought will always be a waste, but with every lone wolf-type unit, you risk facing an opponent with a perfect counter to it. That is why I'd take attack bikes, who are also resilient against autocannons in a way.