I think Hendo was an excellent bowler for England and very underrated. However, though perhaps no yardstick of consistent performance, I'm not sure if he got any fivfers at test level, which some might see as a problem.
I think it also comes down to who you have bowling alongside you. Inevitably batsmen will have to take some of the bowlers on, and it can lead to wickets falling to what you might not term the main strike bowlers. Ridiculous as it might seem, the great Joel Garner might not be rated as the main spearhead of the Windies attack back then. Other attributes (of which there were many) apart, his pace was maybe a bit below the others (though still very sharp) - so maybe the batsmen had to try to take a few more liberties with him than was wise?
Garner wasn't as fast as the other Windies quicks, but because of his 6'8" height and albatross arms he delivered the ball from the most awkward height imagineable.
He was devilishly hard to score off according to the likes of Allan Border and other retired test players.
Hendrick never took a five for, although he took four fers many times. He was simply unlucky in that he was never really a favourite of the selectors.
In teh summer of 1978, Pakistan sent a team minus all their Packer stars to England and then New Zealand toured after them...two extremely weak teams and this is where Botham made his reputation with centuries and 8 fors in successive test matches...even Chris Old took 4 wickets in 5 balls against the hapless Pakis. The story was the same against NZ.
If Hendrick was selected. he would have cleaned up. In that winters Ashes series in Australia, he took more wickets thank Botham and Old combined to finish the leading English paceman of the tour. The man could seriously bowl.