There are many reasons why your hash could taste shit,
1. the solvent used to extract may not be pure enough to evaporate completely.
2. average erbs.
3. processed too long and have extracted useless waxes, chlorophyl and sugars from the plant matter. (thc and resins dissolve at low temps and rather qyuickly) ime.
4. purging. sometimes it will look done, smell it, heat it and smell it, heat and stir it, cool it several times, check consistency of the oil, it should be thick and stay thick while stirring, if it goes runny while you are only stirring it there's a good chance there is still solvent left in that need extracting. even the slightest amount can make it harsh on the throat, and you will lose all terpenes and taste when you go to light it because more often than not it will ignite the oil if not purged correctly. When dropped off the needle/wire onto your cone it should be able to sit nicely on top like a shiny little solid ball

When purged properly it should be very smooth at first to smoke, but has a very strong bite after you exhale because of the potency, and density of the oil. I have made oil from hash resin before and turned about 6 grams into 1.5 grams of honey, so about 3-4 times stronger than the hash it came from according to mass vs potency. a bit of handy info there