Dijkstra is pretty RNG. You can save him till last, but that means you need to have some silver/gold cards left in your deck. Interestingly, the later you use him, the more consistent he becomes and, at the same time, the less flexible.
Anyhow, there are plenty of cards that can push 30 points, but they all require a setup. First of all, an Igni into Ciri: Nova is worth 30 points, in a realistic scenario. However, I don't like using that example because it doesn't really have a limit; you can Scorch away up to a 100 points, if the stars align. Another example is Forktail eating two beefy Nekkers. If the nekkers are (only) 11 strength, it can lead to a 30 point play. One final example is Natalis + Roach into Commander's Horn for another 30 points. There are plenty of other examples, but I'll leave it at this.